AD7771_17 [ADI]
8-Channel, 24-Bit, Simultaneous Sampling ADC;
| 型号： | AD7771_17 |
| 厂家： | 
ADI |
| 描述： | 8-Channel, 24-Bit, Simultaneous Sampling ADC |
| 文件： | 总99页 (文件大小：1848K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
8-Channel, 24-Bit,
Simultaneous Sampling ADC
AD7771
Data Sheet
voltage from 1 V up to 3.6 V. The analog inputs accept unipolar
(0 V to VREF) or true bipolar ( VREF/2 V) analog input signals with
3.3 V or 1.65 V analog supply voltages, respectively. The analog
inputs can be configured to accept true differential or single-ended
signals to match different sensor output configurations.
FEATURES
8-channel, 24-bit simultaneous sampling ADC
Single-ended or true differential inputs
PGA per channel (gains of 1, 2, 4, and 8)
Low dc input current
4 nA (differential)/ 8 nA (single-ended)
Up to 128 kSPS ODR per channel
Programmable ODRs and bandwidth
SRC for coherent sampling
Sampling rate resolution up to 15.2 × 10−6 SPS
Low latency sinc3 and sinc5 filter paths
Adjustable phase synchronization
Internal 2.5 V reference
Each channel contains an ADC modulator and a sinc3/sinc5, low
latency digital filter. A sample rate converter (SRC) is provided to
allow fine resolution control over the AD7771 output data rate
(ODR). This control can be used in applications where the ODR
resolution is required to maintain coherency with 0.01 Hz
changes in the line frequency. The SRC is programmable through
the serial port interface (SPI). The AD7771 implements two
different interfaces: a data output interface and SPI control
interface. The ADC data output interface is dedicated to trans-
mitting the ADC conversion results from the AD7771 to the
processor. The SPI writes to and reads from the AD7771
configuration registers and for the control and reading of data
from the successive approximation register (SAR) ADC. The SPI
can also be configured to output the Σ-Δ conversion data.
Two power modes
High resolution mode
Low power mode
Optimizes power dissipation and performance
Low resolution SAR ADC for system and chip diagnostics
Power supply
Bipolar ( 1.65 V) or unipolar (3.3 V) supplies
Digital I/O supply: 1.8 V to 3.6 V
Performance temperature range: −40°C to +105°C
Functional temperature range: −40°C to +125°C
Performance
Combined ac and dc performance
107 dB SNR/dynamic range at 32 kSPS in high resolution
mode (sinc5)
−109 dB THD
8 ppm of FSR INL
The AD7771 includes a 12-bit SAR ADC. This ADC can be used
for AD7771 diagnostics without having to decommission one of
the Σ-Δ ADC channels dedicated to system measurement func-
tions. With the use of an external multiplexer, which can be
controlled through the three general-purpose input/output pins
(GPIOs), and signal conditioning, the SAR ADC can validate
the Σ-Δ ADC measurements in applications where functional
safety is required. In addition, the AD7771 SAR ADC includes
an internal multiplexer to sense internal nodes.
The AD7771 contains a 2.5 V reference and reference buffer. The
reference has a typical temperature coefficient of 10 ppm/°C.
15 µV offset error
0.1% FS gain error
10 ppm/°C typical temperature coefficient
The AD7771 offers two modes of operation: high resolution
mode and low power mode. High resolution mode provides a
higher dynamic range while consuming 16.6 mW per channel;
low power mode consumes only 5.25 mW per channel at a
reduced dynamic range specification.
APPLICATIONS
Power quality and measurement applications
General-purpose data acquisition
Electroencephalography (EEG)
Industrial process control
The specified operating temperature range is −40°C to +105°C,
although the device is operational up to +125°C.
GENERAL DESCRIPTION
The AD77711 is an 8-channel, simultaneous sampling analog-to-
digital converter (ADC). Eight full Σ-Δ ADCs are on-chip. The
AD7771 provides an ultralow input current to allow direct sensor
connection. Each input channel has a programmable gain stage
allowing gains of 1, 2, 4, and 8 to map lower amplitude sensor
outputs into the full-scale ADC input range, maximizing the
dynamic range of the signal chain. The AD7771 accepts a VREF
Note that throughout this data sheet, certain terms are used to
refer to either the multifunction pins or a range of pins. The
multifunction pins, such as DCLK0/SDO, are referred to either
by the entire pin name or by a single function of the pin, for
example, DCLK0, when only that function is relevant. In the
case of ranges of pins, AVSSx refers to the following pins:
AVSS1A, AVSS1B, AVSS2A, AVSS2B, AVSS3, and AVSS4.
1 This product is protected by at least U.S. Patent No. 9.432,043.
Rev. 0
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responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rightsof third parties that may result fromits use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
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One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
©2017 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
AD7771* PRODUCT PAGE QUICK LINKS
Last Content Update: 07/28/2017
COMPARABLE PARTS
View a parametric search of comparable parts.
TOOLS AND SIMULATIONS
• AD7770/AD7771/AD7779 Filter Model
• AD7771 CRC Calculator
EVALUATION KITS
• AD7770 / AD7771 / AD7779 Evaluation Board
• AD7770/AD7771/AD7779 IBIS Model
REFERENCE MATERIALS
• AD7771 Evaluation Board
Press
DOCUMENTATION
Application Notes
• Analog Devices Improves Monitoring and Protection of
Smart Grid Transmission and Distribution Equipment
• AN-1388: Coherent Sampling for Power Quality
Measurements Using the AD7779 24-Bit Simultaneous
Sampling Sigma-Delta ADC
DESIGN RESOURCES
• AD7771 Material Declaration
• PCN-PDN Information
• Quality And Reliability
• Symbols and Footprints
• AN-1392: How to Calculate Offset Errors and Input
Impedance in ADC Converters with Chopped Amplifiers
• AN-1393: Translating System Level Protection and
Measurement Requirements to ADC Specifications
• AN-1405: Diagnostic Features on the AD7770 and AD7779
DISCUSSIONS
View all AD7771 EngineerZone Discussions.
Data Sheet
• AD7771: 8-Channel, 24-Bit Simultaneous Sampling ADCs
Data Sheet
SAMPLE AND BUY
User Guides
Visit the product page to see pricing options.
• UG-884: Evaluating the AD7770, AD7771, and AD7779 8-
Channel, 24-Bit, Simultaneous Sampling, Sigma-Delta
ADCs with Power Scaling
TECHNICAL SUPPORT
Submit a technical question or find your regional support
number.
SOFTWARE AND SYSTEMS REQUIREMENTS
• AD7770/AD7771/AD7779 - No-OS Driver
DOCUMENT FEEDBACK
Submit feedback for this data sheet.
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AD7771
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Σ-∆ Output Data............................................................................. 53
ADC Conversion Output—Header and Data ........................ 53
Sample Rate Converter (SRC) (SPI Control Mode) .............. 54
Data Output Interface................................................................ 56
Calculating the CRC Checksum .............................................. 60
Register Summary .......................................................................... 61
Register Details ............................................................................... 65
Channel 0 Configuration Register ........................................... 65
Channel 1 Configuration Register ........................................... 65
Channel 2 Configuration Register ........................................... 66
Channel 3 Configuration Register ........................................... 66
Channel 4 Configuration Register ........................................... 67
Channel 5 Configuration Register ........................................... 67
Channel 6 Configuration Register........................................... 68
Channel 7 Configuration Register ........................................... 68
Disable Clocks to ADC Channel Register .............................. 69
Channel 0 Sync Offset Register ................................................ 69
Channel 1 Sync Offset Register ................................................ 69
Channel 2 Sync Offset Register ................................................ 69
Channel 3 Sync Offset Register ................................................ 70
Channel 4 Sync Offset Register ................................................ 70
Channel 5 Sync Offset Register ................................................ 70
Channel 6 Sync Offset Register ................................................ 70
Channel 7 Sync Offset Register ................................................ 70
General User Configuration 1 Register................................... 71
General User Configuration 2 Register................................... 72
General User Configuration 3 Register................................... 73
Data Output Format Register ................................................... 73
Main ADC Meter and Reference Mux Control Register ...... 74
Global Diagnostics Mux Register............................................. 75
GPIO Configuration Register................................................... 75
GPIO Data Register.................................................................... 76
Buffer Configuration 1 Register............................................... 76
Buffer Configuration 2 Register............................................... 76
Channel 0 Offset Upper Byte Register..................................... 77
Channel 0 Offset Middle Byte Register................................... 77
Channel 0 Offset Lower Byte Register..................................... 77
Channel 0 Gain Upper Byte Register....................................... 77
Channel 0 Gain Middle Byte Register..................................... 77
Channel 0 Gain Lower Byte Register....................................... 78
Applications....................................................................................... 1
General Description ......................................................................... 1
Revision History ............................................................................... 3
Functional Block Diagram .............................................................. 4
Specifications..................................................................................... 5
DOUTx Timing Characterististics............................................. 9
SPI Timing Characterististics ................................................... 10
Synchronization Pins and Reset Timing Characteristics...... 11
SAR ADC Timing Characterististics ....................................... 12
GPIO SRC Update Timing Characterististics......................... 12
Absolute Maximum Ratings.......................................................... 13
Thermal Resistance .................................................................... 13
ESD Caution................................................................................ 13
Pin Configuration and Function Descriptions........................... 14
Typical Performance Characteristics ........................................... 17
Terminology .................................................................................... 32
Theory of Operation ...................................................................... 34
Analog Inputs.............................................................................. 34
Transfer Function ....................................................................... 35
Core Signal Chain....................................................................... 36
Capacitive PGA........................................................................... 36
Internal Reference and Reference Buffers............................... 36
Integrated LDOs ......................................................................... 37
Clocking and Sampling.............................................................. 37
Digital Reset and Synchronization Pins .................................. 37
Digital Filtering........................................................................... 38
Shutdown Mode.......................................................................... 38
Controlling the AD7771............................................................ 39
Pin Control Mode....................................................................... 39
SPI Control.................................................................................. 42
Digital SPI.................................................................................... 44
RMS Noise and Resolution............................................................ 47
High Resolution Mode............................................................... 47
Low Power Mode........................................................................ 48
Diagnostics and Monitoring ......................................................... 49
Self Diagnostics Error................................................................ 49
Monitoring Using the AD7771 SAR ADC (SPI Control
Mode)........................................................................................... 50
Σ-Δ ADC Diagnostics (SPI Control Mode)............................ 52
Rev. 0 | Page 2 of 98
Data Sheet
AD7771
Channel 1 Offset Upper Byte Register .....................................78
Channel 1 Offset Middle Byte Register....................................78
Channel 1 Offset Lower Byte Register .....................................78
Channel 1 Gain Upper Byte Register........................................78
Channel 1 Gain Middle Byte Register......................................79
Channel 1 Gain Lower Byte Register........................................79
Channel 2 Offset Upper Byte Register .....................................79
Channel 2 Offset Middle Byte Register....................................79
Channel 2 Offset Lower Byte Register .....................................79
Channel 2 Gain Upper Byte Register........................................80
Channel 2 Gain Middle Byte Register......................................80
Channel 2 Gain Lower Byte Register........................................80
Channel 3 Offset Upper Byte Register .....................................80
Channel 3 Offset Middle Byte Register....................................80
Channel 3 Offset Lower Byte Register .....................................81
Channel 3 Gain Upper Byte Register........................................81
Channel 3 Gain Middle Byte Register......................................81
Channel 3 Gain Lower Byte Register........................................81
Channel 4 Offset Upper Byte Register .....................................81
Channel 4 Offset Middle Byte Register....................................82
Channel 4 Offset Lower Byte Register .....................................82
Channel 4 Gain Upper Byte Register........................................82
Channel 4 Gain Middle Byte Register......................................82
Channel 4 Gain Lower Byte Register........................................82
Channel 5 Offset Upper Byte Register .....................................83
Channel 5 Offset Middle Byte Register....................................83
Channel 5 Offset Lower Byte Register .....................................83
Channel 5 Gain Upper Byte Register........................................83
Channel 5 Gain Middle Byte Register......................................83
Channel 5 Gain Lower Byte Register........................................84
Channel 6 Offset Upper Byte Register .....................................84
Channel 6 Offset Middle Byte Register....................................84
Channel 6 Offset Lower Byte Register .....................................84
Channel 6 Gain Upper Byte Register........................................84
Channel 6 Gain Middle Byte Register......................................85
Channel 6 Gain Lower Byte Register .......................................85
Channel 7 Offset Upper Byte Register .....................................85
Channel 7 Offset Middle Byte Register....................................85
Channel 7 Offset Lower Byte Register .....................................85
Channel 7 Gain Upper Byte Register .......................................86
Channel 7 Gain Middle Byte Register......................................86
Channel 7 Gain Lower Byte Register .......................................86
Channel 0 Status Register ..........................................................86
Channel 1 Status Register ..........................................................87
Channel 2 Status Register ..........................................................87
Channel 3 Status Register ..........................................................88
Channel 4 Status Register ..........................................................88
Channel 5 Status Register ..........................................................89
Channel 6 Status Register ..........................................................89
Channel 7 Status Register ..........................................................90
Channel 0/Channel 1 DSP Errors Register..............................90
Channel 2/Channel 3 DSP Errors Register..............................91
Channel 4/Channel 5 DSP Errors Register..............................91
Channel 6/Channel 7 DSP Errors Register..............................92
Channel 0 to Channel 7 Error Register Enable Register .......92
General Errors Register 1...........................................................93
General Errors Register 1 Enable..............................................93
General Errors Register 2...........................................................94
General Errors Register 2 Enable..............................................94
Error Status Register 1................................................................95
Error Status Register 2................................................................95
Error Status Register 3................................................................96
Decimation Rate (N) MSB Register .........................................96
Decimation Rate (N) LSB Register...........................................96
Decimation Rate (IF) MSB Register.........................................96
Decimation Rate (IF) LSB Register ..........................................97
SRC Load Source and Load Update Register..........................97
Outline Dimensions........................................................................98
Ordering Guide ...........................................................................98
REVISION HISTORY
6/2017—Revision 0: Initial Version
Rev. 0 | Page 3 of 98
AD7771
Data Sheet
FUNCTIONAL BLOCK DIAGRAM
AVDD1x REF_OUT
REFx+ REFx–
AVDD2x AREGxCAP
IOVDD
DREGCAP
COMMON-
XTAL1
ANALOG
LDO
DIGITAL
LDO
MODE
VCM
XTAL2/MCLK
SYNC_IN
SYNC_OUT
START
VOLTAGE
CLOCK
MANAGER
2.5V REF
AIN0+
AIN0–
SINC3/
GAIN
OFFSET
SINC5
SRC
PGA
Σ-Δ ADC
280mV p-p
EXT_REF
INT_REF
DCLK
FILTER
DRDY
DOUT3
DOUT2
DOUT1
DOUT0
DATA OUTPUT
SINC3/
SINC5
SRC
GAIN
AIN1+
AIN1–
INTERFACE
PGA
PGA
Σ-Δ ADC
Σ-Δ ADC
Σ-Δ ADC
Σ-Δ ADC
Σ-Δ ADC
Σ-Δ ADC
Σ-Δ ADC
OFFSET
FILTER
REFERENCES
REFERENCES
REFERENCES
REFERENCES
REFERENCES
REFERENCES
REFERENCES
SINC3/
SINC5
SRC
REGISTER MAP
AND
LOGIC CONTROL
AIN2+
AIN2–
GAIN
OFFSET
RESET
FILTER
FORMAT1
SINC3/
SINC5
SRC
AIN3+
AIN3–
GAIN
OFFSET
FORMAT0
PGA
PGA
FILTER
HARDWARE
MODE
CONFIGURATION
MODE3/ALERT
MODE2/GPIO2
MODE1/GPIO1
MODE0/GPIO0
SINC3/
SINC5
SRC
AIN4+
AIN4–
GAIN
OFFSET
FILTER
SINC3/
SINC5
SRC
AIN5+
AIN5–
GAIN
OFFSET
PGA
PGA
PGA
ALERT/CS
FILTER
DCLK2/SCLK
DCLK1/SDI
DCLK0/SDO
SPI INTERFACE
SINC3/
SINC5
SRC
AIN6+
AIN6–
GAIN
OFFSET
FILTER
SINC3/
SINC5
SRC
AIN7+
AIN7–
GAIN
OFFSET
FILTER
AUXAIN+
AUXAIN–
AD7771
SAR ADC
DIAGNOSTIC
INPUTS
AVSSx
AVDD4
CONVST_SAR
Figure 1.
Rev. 0 | Page 4 of 98
Data Sheet
AD7771
SPECIFICATIONS
AVDD1x = 1.65 V, AVSSx1 = −1.65 V (dual supply operation), AVDD1x = 3.3 V, AVS Sx = analog ground (AGND) (single-supply operation),
AVDD2x − AVSSx = 2.2 V to 3.6 V; IOVDD = 1.8 V to 3.6 V; DGND = 0 V, REFx+/REFx− = 2.5 V AVSSx (internal/external), master clock
(MCLK) = 8192 kHz for high resolution mode and 4096 kHz for low power mode, ODR = 128 kSPS for high resolution mode and 32 kSPS
for low power mode; all specifications at TMIN to TMAX, unless otherwise noted.
Table 1.
Parameter
Test Conditions/Comments
Min
Typ
Max
VREF/PGAGAIN
0 to VREF/PGAGAIN
AVDD1x − 0.10
Unit
ANALOG INPUTS
Differential Input Voltage Range
Single-Ended Input Voltage Range
AINx Common-Mode Input Range
VREF = (REFx+ − REFx−)
V
V
V
AVSSx + 0.10 (AVDD1x +
AVSSx)/2
Absolute AINx Voltage Limits
DC Input Current
AVSSx + 0.10
AVDD1x − 0.10
V
Differential
High resolution mode
Low power mode
4
1
nA
nA
Single-Ended
High resolution mode
Low power mode
8
2
nA
nA
Input Current Drift
AC Input Capacitance
50
8
pA/°C
pF
PROGRAMMABLE GAIN AMPLIFIER (PGA)
Gain Settings (PGAGAIN
)
1, 2, 4, or 8
Bandwidth
Small Signal
High resolution mode
Low power mode
2
512
MHz
kHz
Large Signal
High resolution mode
Low power mode
See Figure 39, Figure 40, and Figure 44
See Figure 42, Figure 43, and Figure 47
REFERENCE
Internal
Initial Accuracy
Temperature Coefficient
REF_OUT, TA = 25°C
Line regulation
2.495
−10
2.5
10
2.505
38
+10
V
ppm/°C
mA
dB
µV/mA
µV rms
nV/√Hz
ms
Reference Load Current, IL
DC Power Supply Rejection
Load Regulation, ∆VOUT/∆IL
Voltage Noise, eN p-p
Voltage Noise Density, eN
Turn On Settling Time
95
100
6.8
273.5
1.5
0.1 Hz to 10 Hz
1 kHz, 2.5 V reference
100 nF
External
Input Voltage
Buffer Headroom
REFx− Input Voltage
Average REFx Input Current
VREF = (REFx+ − REFx−)
Current per channel
1
2.5
AVDD1x
AVDD1x − 0.1
AVDD1x − REFx+
V
V
V
AVSSx + 0.1
AVSSx
Reference buffer disabled,
high resolution mode
Reference buffer precharge mode
(pre-Q), high resolution mode
Reference buffer disabled,
low power mode
Reference buffer pre-Q,
low power mode
Reference buffer enabled,
high resolution mode
Reference buffer enabled,
low power mode
18
µA/V
nA/V
µA/V
nA/V
nA/V
nA/V
600
4.5
100
12
5
Rev. 0 | Page 5 of 98
AD7771
Data Sheet
Parameter
Test Conditions/Comments
Min
Typ
Max
Unit
TEMPERATURE RANGE
Specified Performance
Functional2
TMIN to TMAX
TMIN to TMAX
−40
−40
+105
+125
°C
°C
TEMPERATURE SENSOR
Accuracy
2
°C
DIGITAL FILTER RESPONSE
Group Delay
Settling Time
See the SRC Group Delay section
See the Settling Time section
See the SRC Bandwidth section
See the SRC Bandwidth section
Pass Band
−0.1 dB
−3 dB
Decimation Rate
Sinc3
Sinc5
16
16
4095.99
2048
CLOCK SOURCE
Frequency
High resolution mode
Low power mode
0.655
1.3
45:55
8.192
4.096
55:45
MHz
MHz
%
Duty Cycle
Σ-Δ ADC
50:50
Speed and Performance
Resolution
24
Bits
ODR
High resolution mode
Low power mode
Sinc3, up to 24 kSPS
Sinc5
128
32
kSPS
kSPS
Bits
No Missing Codes
24
24
Bits
AC Accuracy
Dynamic Range
128 kSPS
32 kSPS
16 kSPS
4 kSPS
32 kSPS
Shorted inputs, PGAGAIN = 1
High resolution mode (sinc5)
High resolution mode (sinc5)
High resolution mode (sinc3)
High resolution mode (sinc3)
Low power mode (sinc5)
95
107
105.9
116
94.5
106.5
95.8
111.8
−109
−105
106
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
8 kSPS
Low power mode (sinc5)
8 kSPS
Low power mode (sinc3)
2 kSPS
Low power mode (sinc3)
Total Harmonic Distortion (THD)
−0.5 dBFS, high resolution mode
−0.5 dBFS, low power mode
Signal-to-Noise-and-Distortion Ratio fIN = 60 Hz
(SINAD)
Spurious-Free Dynamic Range
(SFDR)
Intermodulation Distortion (IMD)
High resolution mode, 16 kSPS,
PGAGAIN = 1
fA = 50 Hz, fB = 51 Hz,
high resolution mode
fA = 50 Hz, fB = 51 Hz,
low power mode
132
dB
dB
dB
−125
−105
−90
DC Power Supply Rejection
DC Common-Mode Rejection Ratio
Crosstalk
AVDD1x = 3.3 V
dB
dB
dB
80
−120
DC ACCURACY
Integral Nonlinearity (INL)
High Resolution
Endpoint method
PGAGAIN = 1
8
4
15
15
ppm of
FSR
ppm of
FSR
Other PGA gains
Rev. 0 | Page 6 of 98
Data Sheet
AD7771
Parameter
Test Conditions/Comments
Min
Typ
Max
Unit
Low Power
PGAGAIN = 1
9
17
ppm of
FSR
Other PGA gains
Over time
6
15
90
ppm of
FSR
µV
µV/°C
µV/1000
hours
Offset Error
Offset Error Drift
15
0.25
−2
Offset Matching
Gain Error
Gain Error Drift vs. Temperature
Gain Matching
25
0.1
0.75
0.1
µV
% FS
ppm/°C
%
PGAGAIN = 1
SAR ADC
Speed and Performance
Resolution
Analog Input Range
Analog Input Common-Mode Range
12
Bits
V
V
AVSS4 + 0.1
AVSS4 + 0.1
AVDD4 − 0.1
AVDD4 − 0.1
(AVDD4 +
AVSS4)/2
Analog Input Current
100
nA
Throughput
DC Accuracy
INL
Differential Nonlinearity (DNL)
Offset
Gain
256
1
kSPS
Differential mode
1.5
LSB
LSB
LSB
LSB
No missing codes (12-bit)
−0.99
1
12
AC Performance
Signal-to-Noise Ratio (SNR)
THD
1 kHz
1 kHz
66
−81
dB
dB
VCM PIN
Output (VCM)
(AVDD1x +
AVSSx)/2
V
Load Current, IL
Load Regulation, ∆VOUT/∆IL
Short-Circuit Current
LOGIC INPUTS
Input Voltage
High, VIH
Low, VIL
Hysteresis
Input Currents
LOGIC OUTPUTS3
Output Voltage
High, VOH
1
12
5
mA
mV/mA
mA
0.7 × IOVDD
−10
V
V
V
µA
0.4
0.1
+10
IOVDD ≥ 3 V, ISOURCE = 1 mA
2.3 V ≤ IOVDD < 3 V,
ISOURCE = 500 µA
0.8 × IOVDD
0.8 × IOVDD
V
V
IOVDD < 2.3 V, ISOURCE = 200 µA
IOVDD ≥ 3 V, ISINK = 2 mA
2.3 V ≤ IOVDD < 3 V, ISINK = 1 mA
IOVDD < 2.3 V, ISINK = 100 µA
Floating state
0.8 × IOVDD
V
V
V
V
µA
pF
Low, VOL
0.4
0.4
0.4
+10
Leakage Current
Output Capacitance
−10
Floating state
10
Σ-Δ ADC Data Output Coding
SAR ADC Data Output Coding
Twos complement
Binary
Rev. 0 | Page 7 of 98
AD7771
Data Sheet
Parameter
Test Conditions/Comments
Min
Typ
Max
Unit
POWER SUPPLIES
AVDD1x − AVSSx
IAVDD1x
All Σ-Δ channels enabled
3.0
3.6
V
4, 5
Reference buffer pre-Q, VCM
enabled, internal reference
enabled
High resolution mode
Low power mode
18.3
5
23.7
6.4
mA
mA
Reference buffer enabled, VCM
enabled, internal reference
enabled
High resolution mode
Low power mode
20.5
5.5
26.7
7.1
mA
mA
Reference buffer disabled, VCM
disabled, internal reference
disabled
High resolution mode
Low power mode
14.3
3.9
18.8
5.1
3.6
10.65
4
3.6
2
10
0
3.6
17
5.5
14.2
4.9
mA
mA
V
mA
mA
V
mA
µA
V
AVDD2x − AVSSx
IAVDD2x
2.2
3
High resolution mode
Low power mode
10.2
3.8
AVDD4 − AVSSx
IAVDD4
SAR enabled
SAR disabled
1.7
1
AVSSx − DGND
IOVDD − DGND
IIOVDD
−1.8
1.8
V
High resolution mode (sinc5)
Low power mode (sinc5)
High resolution mode (sinc3)
Low power mode (sinc3)
14.3
4.6
12.2
2.2
mA
mA
mA
mA
Power Dissipation6
Internal buffers bypassed, internal
reference disabled, internal
oscillator disabled, SAR disabled
High Resolution Mode
Low Power Mode
Power-Down
128 kSPS
32 kSPS
All ADCs disabled
133
42
530
153
48.5
mW
mW
µW
1 AVSSx refers to the following pins: AVSS1A, AVSS1B, AVSS2A, AVSS2B, AVDD3, and AVSS4. This term is used throughout the data sheet.
2 At temperatures higher than 105°C, the device can be operated normally, though slight degradation on the maximum/minimum specifications is expected because
these specifications are only guaranteed up to 105°C. See the Typical Performance Characteristics section for plots showing the typical performance of the device at
high temperatures.
3 The SDO pin and the DOUTx pin are configured in the default mode of strength.
4 AVDD1x = 3.3 V, AVSSx = GND = ground, IOVDD = 1.8 V, CMOS clock.
5 Disabling either the VCM pin or the internal reference results in a 40 µA typical current consumption reduction.
6 Power dissipation is calculated using the maximum supply voltage, 3.6 V.
Rev. 0 | Page 8 of 98
Data Sheet
AD7771
DOUTx TIMING CHARACTERISTISTICS
AVDD1x = 1.65 V, AVSSx1 = −1.65 V (dual supply operation), AVDD1x = 3.3 V, AVSSx = AGND (single-supply operation), AVDD2 −
AVSSx = 2.2 V to 3.6 V; IOVDD = 1.8 V to 3.6 V; DGND = 0 V, REFx+/REFx− = 2.5 V internal/external, MCLK = 8192 kHz; all
specifications at TMIN to TMAX, unless otherwise noted.
Table 2.
Parameter
Description2
Test Conditions/Comments
Min
0.655
60
Typ
Max
Unit
MHz
ns
t1
t2
t3
t4
t5
t6
t7
t8
t9
t10
t11
MCLK frequency
MCLK low time
MCLK high time
DCLK high time
DCLK low time
MCLK falling edge to DCLK rising edge
MCLK falling edge to DCLK falling edge
50:50
8.192
60
121
121
ns
ns
ns
ns
ns
ns
MCLK/2
MCLK/2
45
45
DRDY
DRDY
2
DCLK rising edge to
DCLK rising edge to
DOUTx setup time
DOUTx hold time
rising edge
falling edge
1
ns
20
20
ns
ns
1 AVSSx refers to the following pins: AVSS1A, AVSS1B, AVSS2A, AVSS2B, AVSS3, and AVSS4. This term is used throughout the data sheet.
2 All input signals are specified with tR = tF = 1 ns/V (10% to 90% of IOVDD) and timed from a voltage level of (VIL + VIH)/2.
t1
t2
t3
MCLK
DCLK
t6
t4
t5
t7
t8
t9
DRDY
DOUTx
LSB
MSB
MSB – 1
LSB + 1
LSB
t10
t11
Figure 2. Data Interface Timing Diagram
Rev. 0 | Page 9 of 98
AD7771
Data Sheet
SPI TIMING CHARACTERISTISTICS
AVDD1x = 1.65 V, AVSSx1 = −1.65 V (dual supply operation), AVDD1x = 3.3 V, AVSSx = AGND, AVDD2 − AVSSx = 2.2 V to 3.6 V;
IOVDD = 1.8 V to 3.6 V; DGND = 0 V, REFx+/REFx− = 2.5 V (internal/external), MCLK = 8192 kHz; all specifications at TMIN to TMAX
unless otherwise noted.
,
Table 3.
Parameter
Description2
Test Conditions/Comments
Min
Typ
Max
Unit
MHz
ns
t12
t13
t14
t15
t16
t17
t18
t19
t20
t21
t22A
t22B
t23
t24
t25
SCLK period
SCLK low time
SCLK high time
SCLK rising edge to CS falling edge
CS falling edge to SCLK rising edge
SCLK rising edge to CS rising edge
CS rising edge to SCLK rising edge
Minimum CS high time
SDI setup time
50:50
30
7
7
ns
ns
10
10
10
10
10
5
ns
ns
ns
ns
ns
ns
ns
SDI hold time
5
CS falling edge to SDO enable (SPI = Mode 0)
SCLK falling edge to SDO enable (SPI = Mode 1)
SDO setup time
SDO hold time
CS rising edge to SDO disable
30
49
10
10
30
ns
ns
ns
ns
1 AVSSx refers to the following pins: AVSS1A, AVSS1B, AVSS2A, AVSS2B, AVSS3, and AVSS4. This term is used throughout the data sheet.
2 All input signals are specified with tR = tF = 1 ns/V (10% to 90% of IOVDD) and timed from a voltage level of (VIL + VIH)/2.
t19
CS
t17
t15
t16
t13
t14
t18
SCLK
SDI
t20
t12
MSB
MSB
MSB – 1
LSB + 1
LSB
t22A
t21
SDO
MSB – 1
LSB + 1
LSB
t22B
t25
t24
t23
Figure 3. SPI Control Interface Timing Diagram
Rev. 0 | Page 10 of 98
Data Sheet
AD7771
SYNCHRONIZATION PINS AND RESET TIMING CHARACTERISTICS
AVDD1x = 1.65 V, AVSSx1 = −1.65 V (dual supply operation), AVDD1x = 3.3 V, AVSSx = AGND, AVDD2 − AVSSx = 2.2 V to 3.6 V;
IOVDD = 1.8 V to 3.6 V; DGND = 0 V, REFx+/REFx− = 2.5 V (internal/external), MCLK = 8192 kHz; all specifications at TMIN to TMAX
unless otherwise noted.
,
Table 4.
Parameter
Description2
Test Conditions/Comments
Min
Typ Max Unit
t26
START setup time
10
ns
ns
ns
ns
ns
µs
µs
ns
ms
t27
START hold time
MCLK
MCLK
10
t28
MCLK falling edge to SYNC_OUT falling edge
SYNC_IN setup time
t29
t30
SYNC_IN hold time
MCLK
145
SYNC_IN rising edge to first DRDY
RESET rising edge to first DRDY
RESET hold time
16 kSPS, high resolution mode
16 kSPS, high resolution mode
tINIT_SYNC_IN
tINIT_RESET
t31
225
2 × MCLK
tPOWER_UP
Start time
tPOWER_UP is not shown in Figure 4
2
1 AVSSx refers to the following pins: AVSS1A, AVSS1B, AVSS2A, AVSS2B, AVSS3, and AVSS4. This term is used throughout the data sheet.
2 All input signals are specified with tR = tF = 1 ns/V (10% to 90% of IOVDD) and timed from a voltage level of (VIL + VIH)/2.
MCLK
START
t26
t27
SYNC_OUT
t28
SYNC_IN
t29
t30
DRDY
tINIT_SYNC_IN
RESET
t31
tINIT_RESET
Figure 4. Synchronization Pins and Reset Control Interface Timing Diagram
Rev. 0 | Page 11 of 98
AD7771
Data Sheet
SAR ADC TIMING CHARACTERISTISTICS
AVDD1x = 1.65 V, AVSSx1 = −1.65 V (dual supply operation), AVDD1x = 3.3 V, AVSSx = AGND, AVDD2 − AVSSx = 2.2 V to 3.6 V;
IOVDD = 1.8 V to 3.6 V; DGND = 0 V, REFx+/REFx− = 2.5 V (internal/external), MCLK = 8192 kHz; all specifications at TMIN to TMAX
unless otherwise noted.
,
Table 5.
Parameter
Description2
Min
1
500
50
Typ
Max
Unit
µs
ns
ns
kSPS
t32
t33
t34
t35
Conversion time
Acquisition time3
Delay time
3.4
Throughput data rate
256
1 AVSSx refers to the following pins: AVSS1A, AVSS1B, AVSS2A, AVSS2B, AVSS3 and AVSS4. This term is used throughout the data sheet.
2 All input signals are specified with tR = tF = 1 ns/V (10% to 90% of IOVDD) and timed from a voltage level of (VIL + VIH)/2.
3 Direct mode enabled. If deglitch mode is enabled, add 1.5/MCLK as described in Table 29.
CS
t33
t32
t34
CONVST_SAR
t35
Figure 5. SAR ADC Timing Diagram
GPIO SRC UPDATE TIMING CHARACTERISTISTICS
AVDD1x = 1.65 V, AVSSx1 = −1.65 V (dual supply operation), AVDD1x = 3.3 V, AVSSx = AGND, AVDD2 − AVSSx = 2.2 V to 3.6 V;
IOVDD = 1.8 V to 3.6 V; DGND = 0 V, REFx+/REFx− = 2.5 V (internal/external), MCLK = 8192 kHz; all specifications TMIN to TMAX
unless otherwise noted.
,
Table 6.
Parameter
Description2
Min
10
MCLK
2 × MCLK
20
Typ
Max
Unit
ns
ns
ns
ns
t36
t37
GPIO2 setup time
GPIO2 hold time—high resolution mode
GPIO2 hold time—low power mode
MCLK rising edge to GPIO1 rising edge time
GPIO0 setup time
t38
t39
t40
5
ns
ns
GPIO0 hold time
MCLK
1 AVSSx refers to the following pins: AVSS1A, AVSS1B, AVSS2A, AVSS2B, AVSS3 and AVSS4. This term is used throughout the data sheet.
2 All input signals are specified with tR = tF = 1 ns/V (10% to 90% of IOVDD) and timed from a voltage level of (VIL + VIH)/2.
MCLK
GPIO2
t36
t37
GPIO1
t38
GPIO0
t39
t40
Figure 6. GPIOs for SRC Update Timing Diagram
Rev. 0 | Page 12 of 98
Data Sheet
AD7771
ABSOLUTE MAXIMUM RATINGS
Stresses at or above those listed under Absolute Maximum
Table 7.
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
Parameter
Rating
Any Supply Pin to AVSSx
AVSSx to DGND
AREGxCAP to AVSSx
DREGCAP to DGND
IOVDD to DGND
IOVDD to AVSSx
−0.3 V to +3.96 V
−1.98 V to +0.3 V
−0.3 V to +1.98 V
−0.3 V to +1.98 V
−0.3 V to +3.96 V
−0.3 V to +5.94 V
−0.3 V to +3.96 V
AVSSx − 0.3 V to AVDD1x + 0.3 V or
3.96 V (whichever is less)
AVSSx − 0.3 V to AVDD1x + 0.3 V or
3.96 V (whichever is less)
AVSSx − 0.3 V to AVDD4 + 0.1 V or
3.96 V (whichever is less)
DGND − 0.3 V to IOVDD + 0.3 V or
3.96 V (whichever is less)
DGND − 0.3 V to IOVDD + 0.3 V or
3.96 V (whichever is less)
DGND − 0.3 V to DREGCAP + 0.3 V
or 1.98 V (whichever is less)
THERMAL RESISTANCE
AVDD4 to AVSSx
Analog Input Voltage
Thermal performance is directly linked to printed circuit board
(PCB) design and operating environment. Close attention to
PCB thermal design is required.
REFx Input Voltage
AUXAIN
Table 8. Thermal Resistance
Package Type
CP-64-151
No Thermal Vias
49 Thermal Vias
θJA
θJB
ΨJT
ΨJB
Unit
Digital Input Voltage to
DGND
Digital Output Voltage to
DGND
30.43
22.62
N/A2
3.17
0.13
0.09
6.59
3.19
°C/W
°C/W
1 Thermal impedance simulated values are based on a JEDEC 2S2P thermal
test board. See JEDEC JESD51.
XTAL1 to DGND
2 N/A means not applicable.
AINx , AUXAIN , and
Digital Input Current
10 mA
ESD CAUTION
Operating Temperature
Range
Junction Temperature,
TJ Maximum
−40°C to +125°C
150°C
Storage Temperature Range −65°C to +150°C
Reflow Soldering
ESD
260°C
2 kV
Field Induced Charged
Device Model (FICDM)
500 V
Rev. 0 | Page 13 of 98
AD7771
Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
AIN0–
AIN0+
AIN1–
1
2
3
4
5
6
7
8
9
48 AIN4–
47 AIN4+
46 AIN5–
45 AIN5+
44 AVSS1B
43 AVDD1B
42 REF2–
41 REF2+
40 AIN6–
AIN1+
AVSS1A
AVDD1A
REF1–
REF1+
AIN2–
AD7771
TOP VIEW
(Not to Scale)
39 AIN6+
38 AIN7–
AIN2+ 10
AIN3– 11
AIN3+ 12
37 AIN7+
MODE0/GPIO0 13
MODE1/GPIO1 14
MODE2/GPIO2 15
MODE3/ALERT 16
36 RESET
35 SYNC_IN
34 SYNC_OUT
33 START
NOTES
1. EXPOSED PAD. CONNECT THE EXPOSED PAD TO AVSSx.
Figure 7. Pin Configuration
Table 9. Pin Function Descriptions
Pin No.
Mnemonic
Type
Direction Description
1
2
3
4
5
AIN0−
AIN0+
AIN1−
AIN1+
Analog input
Analog input
Analog input
Analog input
Supply
Input
Input
Input
Input
Supply
Analog Input Channel 0, Negative.
Analog Input Channel 0, Positive.
Analog Input Channel 1, Negative.
Analog Input Channel 1, Positive.
Negative Front-End Analog Supply for Channel 0 to Channel 3, Typical at −1.65 V
(Dual Supply) and AGND (Single Supply). Connect all the AVSSx pins to the
same potential.
AVSS1A
6
7
AVDD1A
REF1−
Supply
Supply
Input
Positive Front-End Analog Supply for Channel 0 to Channel 3, Typical at
AVSSx + 3.3 V. Connect this pin to AVDD1B.
Negative Reference Input 1 for Channel 0 to Channel 3, Typical at AVSSx.
Connect all the REFx− pins to the same potential.
Reference
8
9
10
11
12
13
REF1+
AIN2−
AIN2+
AIN3−
AIN3+
MODE0/GPIO0
Reference
Input
Input
Input
Input
Input
I/O
Positive Reference Input 1 for Channel 0 to Channel 3, Typical at REF1− + 2.5 V.
Analog Input Channel 2, Negative.
Analog Input Channel 2, Positive.
Analog Input Channel 3, Negative.
Analog Input Channel 3, Positive.
Analog input
Analog input
Analog input
Analog input
Digital I/O
Mode 0 Input in Pin Control Mode (MODE0). See Table 14 for more details.
Configurable General-Purpose Input/Output 0 in SPI Control Mode (GPIO0).
If not in use, connect this pin to DGND or IOVDD.
14
15
16
MODE1/GPIO1
MODE2/GPIO2
MODE3/ALERT
Digital I/O
Digital I/O
Digital I/O
I/O
I/O
I/O
Mode 1 Input in Pin Control Mode (MODE1). See Table 14 for more details.
Configurable General-Purpose Input/Output 1 in SPI Control Mode (GPIO1).
If not in use, connect this pin to DGND or IOVDD.
Mode 2 Input in Pin Control Mode (MODE2). See Table 14 for more details.
Configurable General-Purpose Input/Output 2 in SPI Control Mode (GPIO2).
If not in use, connect this pin to DGND or IOVDD.
Mode 3 Input in Pin Control Mode (MODE3). See Table 14 for more details.
Alert Output in SPI Control Mode (ALERT).
Rev. 0 | Page 14 of 98
Data Sheet
AD7771
Pin No.
Mnemonic
Type
Direction Description
17
CONVST_SAR
Digital input
Input
Σ-Δ Output Interface Selection Pin in Pin Control Mode. See Table 13 for more
details. This pin also functions as the start for the SAR conversion in SPI control
mode.
18
19
ALERT/CS
Digital input
Digital input
Input
Input
Alert Output in Pin Control Mode (ALERT).
Chip Select in SPI Control Mode (CS).
DCLK2/SCLK
Data Clock Frequency Selection Pin 2 in Pin Control Mode (DCLK2). See Table 15
for more details.
SPI Clock in SPI Control Mode (SCLK).
20
21
DCLK1/SDI
DCLK0/SDO
Digital input
Digital output
Input
Data Clock Frequency Selection Pin 1 in Pin Control Mode (DCLK1). See Table 15
for more details.
SPI Data Input in SPI Control Mode (SDI). Connect this pin to DGND if the
device is configured in pin control mode with the SPI as the data output interface.
Data Clock Frequency Selection Pin 0 in Pin Control Mode (DCLK0). See Table 15
for more details.
Output
SPI Data Output in SPI Control Mode (SDO).
Digital Ground.
Digital Low Dropout (LDO) Output. Decouple this pin to DGND with a 1 µF
capacitor.
22
23
DGND
DREGCAP
Supply
Supply
Supply
Output
24
25
26
IOVDD
DOUT3
DOUT2
Supply
Supply
I/O
Digital Levels Input/Output and Digital LDO (DLDO) Supply from 1.8 V to 3.6 V.
IOVDD must not be lower than DREGCAP.
Data Output Pin 3. If the device is configured in daisy-chain mode, this pin
acts as an input pin. See the Daisy-Chain Mode section for more details.
Data Output Pin 2. If the device is configured in daisy-chain mode, this pin
acts as an input pin. See the Daisy-Chain Mode section for more details.
Digital output
Digital output
I/O
27
28
29
30
31
DOUT1
DOUT0
DCLK
Digital output
Digital output
Digital output
Digital output
Clock
Output
Output
Output
Output
Input
Data Output Pin 1.
Data Output Pin 0.
Data Output Clock.
Data Output Ready Pin.
DRDY
XTAL1
Crystal 1 Input Connection. If CMOS is used as a clock source, tie this pin to
DGND. See Table 12 for more details.
32
33
XTAL2/MCLK
START
Clock
Input
Input
Crystal 2 Input Connection (XTAL2). See Table 12 for more details.
CMOS Clock (MCLK). See Table 12 for more details.
Synchronization Pulse. This pin internally synchronizes an external START
asynchronous pulse with MCLK. The synchronize signal is shifted out by the
SYNC_OUT pin. If not in use, tie this pin to DGND. See the Phase Adjustment
section and the Digital Reset and Synchronization Pins section for more details.
Digital input
34
SYNC_OUT
Digital output
Input
Synchronization Signal. This pin generates a synchronous pulse generated
and driven by hardware (via the START pin) or by software (GENERAL_USER_
CONFIG_2, Bit 0). If this pin is in use, it must be wired to the SYNC_IN pin.
See the Phase Adjustment section and the Digital Reset and Synchronization
Pins section for more details.
35
36
SYNC_IN
RESET
Digital input
Digital input
Input
Input
Reset for the Internal Digital Block and Synchronize for Multiple Devices. See
the Digital Reset and Synchronization Pins section for more details.
Asynchronous Reset Pin. This pin resets all registers to their default value. It is
recommended to generate a pulse on this pin after the device is powered up
because a slow slew rate in the supplies may generate an incorrect initialization
in the digital block.
37
38
39
40
41
42
AIN7+
AIN7−
AIN6+
AIN6−
REF2+
REF2−
Analog input
Analog input
Analog input
Analog input
Reference
Input
Input
Input
Input
Input
Input
Analog Input Channel 7, Positive.
Analog Input Channel 7, Negative.
Analog Input Channel 6, Positive.
Analog Input Channel 6, Negative.
Positive Reference Input 2 for Channel 4 to Channel 7, Typical at REF2− + 2.5 V.
Negative Reference Input 2 for Channel 4 to Channel 7, Typical at AVSSx.
Connect all the REFx− pins to the same potential.
Reference
43
AVDD1B
Supply
Supply
Positive Front-End Analog Supply for Channel 4 to Channel 7. Connect this pin
to AVDD1A.
Rev. 0 | Page 15 of 98
AD7771
Data Sheet
Pin No.
Mnemonic
Type
Direction Description
44
AVSS1B
Supply
Supply
Negative Front-End Analog Supply for Channel 4 to Channel 7, Typical at
−1.65 V (Dual Supply) or AGND (Single Supply). Connect all the AVSSx pins to
the same potential.
45
46
47
48
49
AIN5+
AIN5−
AIN4+
AIN4−
REF_OUT
Analog input
Analog input
Analog input
Analog input
Reference
Input
Input
Input
Input
Output
Analog Input Channel 5, Positive.
Analog Input Channel 5, Negative.
Analog Input Channel 4, Positive.
Analog Input Channel 4, Negative.
2.5 V Reference Output. Connect a 100 nF capacitor on this pin if using the
internal reference.
50
51
52
53
54
55
56
57
58
AVSS2B
AREG2CAP
AVDD2B
AVSS3
FORMAT1
FORMAT0
CLK_SEL
VCM
Supply
Supply
Supply
Supply
Digital input
Digital input
Digital input
Analog output Output
Supply
Supply
Output
Supply
Supply
Input
Negative Analog Supply. Connect all the AVSSx pins together.
Analog LDO Output 2. Decouple this pin to AVSS2B with a 1 µF capacitor.
Positive Analog Supply. Connect this pin to AVDD2A.
Negative Analog Ground. Connect all the AVSSx to the same potential.
Output Data Frame 1. See Table 13 for more details.
Output Data Frame 0. See Table 13 for more details.
Select Clock Source. See Table 12 for more details.
Common-Mode Voltage Output, Typical at (AVDD1x + AVSSx)/2.
Analog Supply from 2.2 V to 3.6 V. AVSS2x must not be lower than AREGxCAP.
Connect this pin to AVDD2B.
Input
Input
AVDD2A
Input
59
60
61
AREG1CAP
AVSS2A
AVSS4
Supply
Supply
Supply
Output
Input
Supply
Analog LDO Output 1. Decouple this pin to AVSSx with a 1 µF capacitor.
Negative Analog supply. Connect all the AVSSx pins to the same potential.
Negative SAR Analog Supply and Reference. Connect all AVSSx pins to the same
potential.
62
63
64
AVDD4
AUXAIN+
AUXAIN−
EPAD
Supply
Supply
Input
Input
Input
Positive SAR Analog Supply and Reference Source.
Positive SAR Analog Input Channel.
Negative SAR Analog Input Channel.
Analog input
Analog input
Supply
Exposed Pad. Connect the exposed pad to AVSSx.
Rev. 0 | Page 16 of 98
Data Sheet
AD7771
TYPICAL PERFORMANCE CHARACTERISTICS
10
15
10
5
T
= 25°C
A
T = 25°C
A
GAIN = 1
DIFFERENTIAL INPUT SIGNAL
GAIN = 1
DIFFERENTIAL INPUT SIGNAL
8
6
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
REF
CM
REF
CM
4
2
0
0
–2
–4
–6
–8
–10
CH 0
CH 0
CH 1
CH 2
CH 3
CH 4
CH 5
CH 6
CH 7
–5
–10
–15
CH 1
CH 2
CH 3
CH 4
CH 5
CH 6
CH 7
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Figure 8. INL vs. Input Voltage and Channel at 64 kSPS,
High Resolution Mode
Figure 11. INL vs. Input Voltage and Channel at 16 kSPS,
Low Power Mode
10
8
10
8
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
6
6
4
4
2
2
0
0
–2
–4
–6
–8
–10
–2
–4
–6
–8
–10
T
= 25°C
T
= 25°C
A
A
DIFFERENTIAL V × GAIN
V
V
DIFFERENTIAL V × GAIN
V
V
IN
IN
= 2.5V
= 2.5V
REF
CM
REF
CM
= (AVDD1x + AVSSx) ÷ 2
= (AVDD1x + AVSSx) ÷ 2
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Figure 9. INL vs. Input Voltage and PGA Gain at 64 kSPS,
High Resolution Mode
Figure 12. INL vs. Input Voltage and PGA Gain at 16 kSPS,
Low Power Mode
10
8
10
T
T
T
T
= –40°C
= +25°C
= +105°C
= +125°C
T
T
T
T
= –40°C
= +25°C
= +105°C
= +125°C
A
A
A
A
A
A
A
A
6
5
4
2
0
0
–2
–4
–6
–8
–10
–5
–10
–15
GAIN = 1
DIFFERENTIAL INPUT SIGNAL
GAIN = 1
DIFFERENTIAL INPUT SIGNAL
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
REF
CM
REF
CM
–3
–2
–1
0
1
2
3
–3
–2
–1
0
1
2
3
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Figure 10. INL vs. Input Voltage and Temperature at 64 kSPS,
High Resolution Mode
Figure 13. INL vs. Input Voltage and Temperature at 16 kSPS,
Low Power Mode
Rev. 0 | Page 17 of 98
AD7771
Data Sheet
20
15
10
5
15
10
5
V
V
V
V
V
V
= 1.0V
= 1.5V
= 2.0V
= 2.5V
= 3.0V
= 3.3V
V
V
V
V
V
V
= 1.0V
= 1.5V
= 2.0V
= 2.5V
= 3.0V
= 3.3V
REF
REF
REF
REF
REF
REF
REF
REF
REF
REF
REF
REF
0
0
–5
–10
–15
–5
–10
–15
T
= 25°C
A
GAIN = 1
DIFFERENTIAL INPUT SIGNAL
V
V
T
= 25°C
A
GAIN = 1
DIFFERENTIAL INPUT SIGNAL
V
= (AVDD1x + AVSSx) ÷ 2
= 2.5V
CM
REF
= (AVDD1x + AVSSx) ÷ 2
CM
–20
–4
–3
–2
–1
0
1
2
3
4
–4
–3
–2
–1
0
1
2
3
4
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Figure 14. INL vs. Input Voltage and Reference Voltage (VREF
at 64 kSPS, High Resolution Mode
)
Figure 17. INL vs. Input Voltage and Reference Voltage (VREF
at 16 kSPS, Low Power Mode
)
10
15
V
V
V
= 1.95V
= 1.65V
= 1.35V
V
V
V
= 1.95V
= 1.65V
= 1.35V
CM
CM
CM
CM
CM
CM
8
6
10
5
4
2
0
0
–2
–4
–6
–8
–10
–5
–10
–15
T
= 25°C
T
= 25°C
A
A
GAIN = 1
DIFFERENTIAL INPUT SIGNAL
V
GAIN = 1
DIFFERENTIAL V × GAIN
V
IN
= 2.5V
= 2.5V
REF
REF
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Figure 15. INL vs. Input Voltage and VCM at 64 kSPS,
High Resolution Mode
Figure 18. INL vs. Input Voltage and VCM at 16 kSPS,
Low Power Mode
1000
900
800
700
600
500
400
300
200
100
0
1000
900
800
700
600
500
400
300
200
100
0
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
= 25°C
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
= 25°C
REF
REF
CM
CM
T
T
A
A
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
ADC CODE
ADC CODE
Figure 16. Noise Histogram at 16 kSPS, High Resolution Mode,
Sinc3 Filter Enabled
Figure 19. Noise Histogram at 4 kSPS, Low Power Mode,
Sinc3 Filter Enabled
Rev. 0 | Page 18 of 98
Data Sheet
AD7771
300
300
250
200
150
100
50
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
= 25°C
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
REF
REF
CM
CM
T
T = 25°C
A
A
250
200
150
100
50
GAIN = 1
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 2
GAIN = 4
GAIN = 8
0
0
ADC CODE
ADC CODE
Figure 20. Noise Histogram at 64 kSPS, High Resolution Mode,
Sinc5 Filter Enabled
Figure 23. Noise Histogram at 16 kSPS, Low Power Mode,
Sinc5 Filter Enabled
12
10
8
12
10
8
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
REF
CM
REF
CM
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
6
6
4
4
2
2
0
–40
0
–40
25
105
125
25
105
125
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 21. Noise vs. Temperature at 16 kSPS, High Resolution Mode,
Sinc3 Filter Enabled
Figure 24. Noise vs. Temperature at 4 kSPS, Low Power Mode,
Sinc3 Filter Enabled
18
20
GAIN = 1
GAIN = 2
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
REF
CM
18
16
14
12
10
8
16
GAIN = 4
GAIN = 8
14
12
10
8
6
6
4
4
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
REF
CM
2
2
0
–40
0
–40
25
105
125
25
105
125
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 22. Noise vs. Temperature at 64 kSPS, High Resolution Mode,
Sinc5 Filter Enabled
Figure 25. Noise vs. Temperature at 16 kSPS, Low Power Mode,
Sinc5 Filter Enabled
Rev. 0 | Page 19 of 98
AD7771
Data Sheet
1.6
1.5
1.4
1.3
1.2
1.1
1.0
9.0
8.0
7.0
1.80
1.60
1.40
1.20
1.00
8.00
6.00
4.00
2.00
0
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
V
V
= 2.5V
= (AVDD1x + AVSSx) ÷ 2
= 25°C
REF
REF
6.0
5.0
4.0
3.0
2.0
1.0
0
CM
CM
T = 25°C
T
A
A
DECIMATION = 256
DECIMATION = 256
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
CLOCK FREQUENCY (Hz)
CLOCK FREQUENCY (Hz)
Figure 26. Noise vs. Clock Frequency, High Resolution Mode
Figure 29. Noise vs. Clock Frequency, Low Power Mode
160
700
600
500
400
300
200
100
0
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
140
120
100
80
60
40
20
0
1000
4000
8000
16000
500
2000
4000
8000
ODR (SPS)
ODR (SPS)
Figure 27. Noise vs. ODR, High Resolution Mode, Sinc3 Filter Enabled
Figure 30. Noise vs. ODR, Low Power Mode, Sinc3 Filter Enabled
180
400
GAIN = 1
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 2
160
GAIN = 4
GAIN = 8
350
300
250
200
150
100
50
140
120
100
80
60
40
20
0
0
8000
32000
64000
128000
1000
8000
16000
ODR (SPS)
32000
ODR (SPS)
Figure 28. Noise vs. ODR, High Resolution Mode, Sinc5 Filter Enabled
Figure 31. Noise vs. ODR, Low Power Mode, Sinc5 Filter Enabled
Rev. 0 | Page 20 of 98
Data Sheet
AD7771
10
0
–10
10
0
–10
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
–20
–20
–30
–30
T
V
V
= 25°C
–40
–50
–60
–70
T
V
V
= 25°C
–40
–50
–60
–70
A
A
= 2.5V
= 2.5V
REF
REF
= (AVDD1x + AVSSx) ÷ 2
= (AVDD1x + AVSSx) ÷ 2
CM
CM
INPUT FREQUENCY = 50Hz
INPUT FREQUENCY = 50Hz
–80
–80
–90
–90
–100
–110
–120
–130
–140
–150
–160
–170
–180
–100
–110
–120
–130
–140
–150
–160
–170
–180
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 35. FFT Plot, Low Power Mode at 4 kSPS,
Input Frequency (fIN) = 50 Hz, Sinc3 Filter Enabled
Figure 32. FFT Plot, High Resolution Mode at 16 kSPS,
Input Frequency (fIN) = 50 Hz, Sinc3 Filter Enabled
10
0
–10
–20
–30
–40
–50
–60
–70
10
0
–10
–20
–30
–40
–50
–60
–70
GAIN = 1
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 2
GAIN = 4
GAIN = 8
T
V
V
= 25°C
A
T
V
V
= 25°C
= 2.5V
A
= 2.5V
REF
REF
= (AVDD1x + AVSSx) ÷ 2
= (AVDD1x + AVSSx) ÷ 2
CM
CM
ODR = 32kSPS
ODR = 128kSPS
INPUT FREQUENCY = 50Hz
INPUT FREQUENCY = 50Hz
–80
–80
–90
–90
–100
–110
–120
–130
–140
–150
–160
–170
–180
–100
–110
–120
–130
–140
–150
–160
–170
–180
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 33. FFT Plot, High Resolution Mode at 128 kSPS,
Input Frequency (fIN) = 50 Hz, Sinc5 Filter Enabled
Figure 36. FFT Plot, Low Power Mode at 32 kSPS,
Input Frequency (fIN) = 50 Hz, Sinc5 Filter Enabled
10
0
–10
–20
–30
–40
–50
–60
–70
10
0
–10
–20
–30
–40
–50
–60
–70
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
T
V
V
= 25°C
= 2.5V
A
T = 25°C
A
REF
= (AVDD1x + AVSSx) ÷ 2
INPUT FREQUENCY = 1kHz
V
= 2.5V
REF
V
= (AVDD1x + AVSSx) ÷ 2
INPUT FREQUENCY = 1kHz
CM
CM
–80
–80
–90
–90
–100
–110
–120
–130
–140
–150
–160
–170
–180
–100
–110
–120
–130
–140
–150
–160
–170
–180
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 37. FFT Plot, Low Power Mode at 4 kSPS,
Input Frequency (fIN) = 1 kHz, Sinc3 Filter Enabled
Figure 34. FFT Plot, High Resolution Mode at 16 kSPS,
Input Frequency (fIN) = 1 kHz, Sinc3 Filter Enabled
Rev. 0 | Page 21 of 98
AD7771
Data Sheet
10
0
–10
–20
–30
–40
–50
–60
–70
10
0
–10
–20
–30
–40
–50
–60
–70
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
T
V
V
= 25°C
A
T
V
V
= 25°C
A
= 2.5V
REF
= 2.5V
REF
= (AVDD1x + AVSSx) ÷ 2
CM
= (AVDD1x + AVSSx) ÷ 2
CM
ODR = 32kSPS
ODR = 128kSPS
INPUT FREQUENCY = 1kHz
INPUT FREQUENCY = 1kHz
–80
–90
–80
–90
–100
–110
–120
–130
–140
–150
–160
–170
–180
–100
–110
–120
–130
–140
–150
–160
–170
–180
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 41. FFT Plot, Low Power Mode at 32 kSPS,
Input Frequency (fIN) = 1 kHz, Sinc5 Filter Enabled
Figure 38. FFT Plot, High Resolution Mode at 128 kSPS,
Input Frequency (fIN) = 1 kHz, Sinc5 Filter Enabled
–100
–105
–110
–115
–120
–125
–100
–105
–110
–115
–120
–125
–130
GAIN = 1
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 2
GAIN = 4
GAIN = 8
T
= 25°C
A
GAIN = 1
T
V
V
= 25°C
A
V
V
V
= 2.5V
REF
= 2.5V
REF
= (AVDD1x + AVSSx) ÷ 2
CM
= –0.5dBFS
IN
= –0.5dBFS
IN
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
Figure 42. THD vs. Input Frequency at 16 kSPS, Low Power Mode,
Sinc5 Filter Enabled
Figure 39. THD vs. Input Frequency at 64 kSPS, High Resolution Mode,
Sinc5 Filter Enabled
–100
–100
GAIN = 1
GAIN = 2
GAIN = 1
GAIN = 2
GAIN = 4
–105
GAIN = 4
GAIN = 8
–105
GAIN = 8
T
V
V
= 25°C
A
–110
–115
–120
–125
T
V
V
= 25°C
= 2.5V
A
REF
= –0.5dBFS
–110
–115
–120
–125
= 2.5V
REF
= –0.5dBFS
IN
IN
–130
–135
–130
–135
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
Figure 43. THD vs. Input Frequency at 4 kSPS, Low Power Mode,
Sinc3 Filter Enabled
Figure 40. THD vs. Input Frequency at 16 kSPS, High Resolution Mode,
Sinc3 Filter Enabled
Rev. 0 | Page 22 of 98
Data Sheet
AD7771
–100
–100
–105
–110
–115
–120
–125
–130
–135
–140
GAIN = 1
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 2
GAIN = 4
GAIN = 8
–105
–110
–115
–120
–125
–130
–135
–140
T
A
V
= 25°C
= 2.5V
T
V
= 25°C
A
REF
= 2.5V
REF
INPUT FREQUENCY = 50Hz
INPUT FREQUENCY = 50Hz
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
Figure 44. THD vs. Input Voltage at 64 kSPS, High Resolution Mode
Figure 47. THD vs. Input Voltage at 16 kSPS, Low Power Mode
–90
–90
GAIN = 1
GAIN = 2
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
T
±V
= 25°C
A
REF
GAIN = 4
INPUT FREQUENCY = 50Hz
–95
–95
–100
–105
–110
–115
–120
–125
GAIN = 8
–100
–105
–110
–115
T
±V
= 25°C
A
–120
–125
REF
INPUT FREQUENCY = 50Hz
REFERENCE VOLTAGE (V)
REFERENCE VOLTAGE (V)
Figure 45. THD vs. Reference Voltage at 64 kSPS, High Resolution Mode
Figure 48. THD vs. Reference Voltage at 16 kSPS, Low Power Mode
–100
–100
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
T
V
= 25°C
A
= 2.5V
REF
–102
–104
–106
–108
–110
–112
–114
–116
–118
INPUT FREQUENCY = 50Hz
–105
–110
–115
–120
GAIN = 1
T
V
= 25°C
A
GAIN = 2
GAIN = 4
GAIN = 8
= 2.5V
REF
INPUT FREQUENCY = 50Hz
–125
MCLK FREQUENCY (Hz)
MCLK FREQUENCY (Hz)
Figure 46. THD vs. Master Clock Frequency, High Resolution Mode
Figure 49. THD vs. Master Clock Frequency, Low Power Mode
Rev. 0 | Page 23 of 98
AD7771
Data Sheet
125
120
115
110
105
100
95
120
115
110
105
100
95
90
90
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
T
V
V
= 25°C
T = 25°C
A
A
85
= 2.5V
V
= 2.5V
85
REF
REF
= 0dBFS
IN
= 0dBFS
V
IN
80
1000
80
500
4000
8000
16000
2000
4000
8000
ODR (SPS)
ODR (SPS)
Figure 50. SNR vs. ODR at 16 kSPS, High Resolution Mode
(AVDDx = 3.6 V, IOVDD = 3.6 V)
Figure 53. SNR vs. ODR at 4 kSPS, Low Power Mode
(AVDDx = 3.6 V, IOVDD = 3.6 V)
115
110
105
100
95
120
GAIN = 1
T
V
V
= 25°C
A
GAIN = 2
GAIN = 4
GAIN = 8
= 2.5V
REF
115
110
105
100
95
= 0dBFS
IN
T
V
V
= 25°C
A
= 2.5V
REF
= 0dBFS
IN
90
90
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
85
85
80
8000
80
1000
32000
64000
128000
8000
16000
32000
ODR (SPS)
ODR (SPS)
Figure 51. SNR vs. ODR at 64 kSPS, High Resolution Mode
(AVDDx = 3.6 V, IOVDD = 3.6 V)
Figure 54. SNR vs. ODR at 16 kSPS, Low Power Mode
(AVDDx = 3.6 V, IOVDD = 3.6 V)
108
108
106
104
102
100
98
T
= 25°C
A
T
= 25°C
A
ODR = 4kSPS
ODR = 16kSPS
106
104
102
100
98
96
94
1
2
4
8
1
2
4
8
PGA GAIN
PGA GAIN
Figure 52. Dynamic Range vs. PGA Gain at 16 kSPS,
High Resolution Mode
Figure 55. Dynamic Range vs. PGA Gain at 4 kSPS,
Low Power Mode
Rev. 0 | Page 24 of 98
Data Sheet
AD7771
104
102
100
98
105
100
95
T
= 25°C
T = 25°C
A
ODR = 16kSPS
A
ODR = 64kSPS
96
94
92
90
90
88
85
86
84
82
80
1
2
4
8
1
2
4
8
PGA GAIN
PGA GAIN
Figure 56. Dynamic Range vs. PGA Gain at 64 kSPS,
High Resolution Mode
Figure 59. Dynamic Range vs. PGA Gain at 16 kSPS,
Low Power Mode
0
–5
0
–5
10
T
V
V
= 25°C
T = 25°C
A
A
= 2.5V
V
= 2.5V
REF
REF
= 0V
V = 0V
IN
IN
SUPPLY = AVDD1x = 3.3V
SUPPLY = AVDD1x = 3.3V
–10
–15
–20
–25
–30
–35
–40
–15
–20
–25
–30
–35
CH 0
CH 1
CH 2
CH 3
CH 4
CH 5
CH 6
CH 7
CH 0
CH 1
CH 2
CH 3
CH 4
CH 5
CH 6
CH 7
1
2
4
8
1
2
4
8
PGA GAIN
PGA GAIN
Figure 57. Offset Error vs. PGA Gain at 64 kSPS,
High Resolution Mode
Figure 60. Offset Error vs. PGA Gain at 16 kSPS,
Low Power Mode
0
–5
0
–5
–10
–15
–20
–25
–10
–15
–20
–25
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
T
V
V
= 25°C
A
= 2.5V
REF
= 0V
IN
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
T
V
V
= 25°C
A
= 2.5V
REF
= 0V
IN
3.0
3.3
3.6
3.0
3.3
3.6
AVDD1x SUPPLY
AVDD1x SUPPLY
Figure 58. Offset Error vs. AVDD1x Supply,
High Resolution Mode
Figure 61. Offset Error vs. AVDD1x Supply,
Low Power Mode
Rev. 0 | Page 25 of 98
AD7771
Data Sheet
40
45
40
35
30
25
20
15
10
5
AVDD1x = 3.3V
30
20
10
0
–10
–20
–30
–40
–50
CH 0
CH 1
CH 2
CH 3
CH 4
CH 5
CH 6
CH 7
0
–5
–10
–15
–20
0
168
500
1000
–40
–20
0
20
40
60
80
100
120
TEMPERATURE (°C)
TIME (Hours)
Figure 65. Gain Error Drift vs. Time
Figure 62. Offset Drift vs. Temperature
0.017
0.008
0
0.017
0.008
0
CH 0
TEMPERATURE = 25°C
GAIN = 1
CH 0
CH 1
CH 2
CH 3
CH 4
CH 5
CH 6
CH 7
TEMPERATURE = 25°C
GAIN = 1
CH 1
CH 2
CH 3
CH 4
CH 5
CH 6
CH 7
V
V
= 2.5V
= 0dBFS
V
V
= 2.5V
REF
REF
= 0dBFS
IN
IN
–0.008
–0.017
–0.026
–0.035
–0.043
–0.008
–0.017
–0.026
–0.035
–0.043
3.0
3.3
AVDD1x SUPPLY (V)
3.6
3.0
3.3
AVDD1x SUPPLY (V)
3.6
Figure 66. Gain Error vs. AVDD1x Supply, Low Power Mode
Figure 63. Gain Error vs. AVDD1x Supply, High Resolution Mode
0.017
0.011
0.005
0
0.017
CH 0
CH 0
CH 1
CH 2
CH 3
CH 4
CH 5
CH 6
CH 7
AVDD1x = 3.3V
AVDD1x = 3.3V
CH 1
CH 2
CH 3
CH 4
CH 5
CH 6
CH 7
V
V
= 2.5V
= 0dBFS
V
= 2.5V
REF
REF
0.011
0.005
0
V = 0dBFS
IN
IN
–0.005
–0.011
–0.017
–0.023
–0.029
–0.035
–0.400
–0.005
–0.011
–0.017
–0.023
–0.029
–0.035
–0.400
–40
25
105
125
–40
25
105
125
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 67. Gain Error vs. Temperature, Low Power Mode
Figure 64. Gain Error vs. Temperature, High Resolution Mode
Rev. 0 | Page 26 of 98
Data Sheet
AD7771
0.09
4
3
TEMPERATURE = 25°C
AVDD1x = 3.3V
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
V
V
= 2.5V
= 0dBFS
REF
2
IN
1
0
HIGH RESOLUTION
LOW POWER
–1
–2
–3
–4
–5
–6
1
2
4
8
–40
25
105
125
PGA GAIN
TEMPERATURE (°C)
Figure 68. Channel Gain Mismatch
Figure 71. Internal Reference Voltage Drift
0.008
0.006
0.004
0.002
0
0.006
0.004
0.002
0
V
V
= 2.5V
= –0.5dBFS
REF
IN
SUPPLY = AVDD1x = 3.3V
–0.002
–0.004
–0.006
–0.008
–0.010
–0.002
–0.004
–0.006
–0.008
CH 0
CH 1
CH 2
CH 3
CH 4
CH 0
CH 1
CH 2
CH 3
CH 4
CH 5
CH 6
CH 7
V
V
= 2.5V
= –0.5dBFS
REF
CH 5
CH 6
CH 7
IN
SUPPLY = AVDD1x = 3.3V
–40 –30 –20 –10
0
10 20 30 40 50 60 70 80 90 100 110 125
–40 –30 –20 –10
0
10 20 30 40 50 60 70 80 90 100 110 125
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 69. Total Unadjusted Error (TUE) (as Percent of Input) vs. Temperature,
High Resolution Mode
Figure 72. Total Unadjusted Error (TUE) (as Percent of Input) vs.
Temperature, Low Power Mode
3
1.0
AINx+, V
AINx–, V
= 1.95V
= 1.95V
= 1.35V
= 1.35V
CM
CM
AINx+, V
AINx–, V
= 1.95V
= 1.95V
= 1.35V
= 1.35V
CM
CM
0.8
0.6
2
1
AINx+; V
CM
CM
AINx+; V
CM
CM
AINx–, V
AINx–, V
0.4
0
0.2
–1
–2
–3
–4
–5
0
–0.2
–0.4
–0.6
–0.8
V
= 2.5V
V
= 2.5V
REF
SUPPLY = AVDD1x = 3.3V
REF
SUPPLY = AVDD1x = 3.3V
–2.5 –2.0 –1.5 –1.0 –0.5
0
0.5
1.0
1.5
2.0
2.5
–2.5 –2.0 –1.5 –1.0 –0.5
0
0.5
1.0
1.5
2.0
2.5
DIFFERENTIAL INPUT VOLTAGE ((AINx+) – (AINx–))
DIFFERENTIAL INPUT VOLTAGE ((AINx+) – (AINx–))
Figure 70. Input Current vs. Differential Input Voltage,
High Resolution Mode
Figure 73. Input Current vs. Differential Input Voltage,
Low Power Mode
Rev. 0 | Page 27 of 98
AD7771
Data Sheet
10
6
4
AIN0+
AIN0–
AIN2+
AIN2–
AIN0+
AIN0–
AIN2+
AIN2–
5
2
0
0
–2
–4
–6
–8
–5
–10
V
= 2.5V
= 2.5V
SUPPLY = AVDD1x = 3.3V
V
V
= 2.5V
= 2.5V
REF
REF
V
IN
IN
SUPPLY = AVDD1x = 3.3V
–15
–60 –40 –20
0
20
40
60
80
100 120 140
–60 –40 –20
0
20
40
60
80
100 120 140
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 74. Absolute Input Current vs. Temperature, High Resolution Mode
Figure 77. Absolute Input Current vs. Temperature, Low Power Mode
4
1.0
AINx+ – AINx–, V
AINx+ – AINx–, V
= 1.95V
= 1.35V
CM
CM
AINx+ – AINx–, V
AINx+ – AINx–, V
= 1.95V
= 1.35V
CM
CM
0.8
0.6
3
2
0.4
1
0.2
0
0
–0.2
–0.4
–0.6
–0.8
–1.0
–1
–2
–3
–4
V
= 2.5V
REF
SUPPLY = AVDD1x = 3.3V
V
= 2.5V
REF
SUPPLY = AVDD1x = 3.3V
–2.5 –2.0 –1.5 –1.0 –0.5
0
0.5
1.0
1.5
2.0
2.5
–2.5 –2.0 –1.5 –1.0 –0.5
0
0.5
1.0
1.5
2.0
2.5
DIFFERENTIAL INPUT VOLTAGE ((AINx+) – (AINx–))
DIFFERENTIAL INPUT VOLTAGE ((AINx+) – (AINx–))
Figure 75. Differential Input Current vs. Differential Input Voltage,
High Resolution Mode
Figure 78. Differential Input Current vs. Differential Input Voltage,
Low Power Mode
14
12
V
V
= 2.5V
REF
= 2.5V
V
V
= 2.5V
REF
= 2.5V
IN
IN
12
10
8
SUPPLY = AVDD1x = 3.3V
SUPPLY = AVDD1x = 3.3V
10
8
6
6
4
4
2
2
0
0
–40
–60 –40 –20
0
20
40
60
80
100 120 140
–20
0
20
40
60
80
100
120
140
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 76. Differential Input Current vs. Temperature,
High Resolution Mode
Figure 79. Differential Input Current vs. Temperature,
Low Power Mode
Rev. 0 | Page 28 of 98
Data Sheet
AD7771
0
0
–20
GAIN = 1
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
V
= 1.65V + 100mV p-p
V
= 1.65V + 100mV p-p
CM
CM
GAIN = 2
GAIN = 4
GAIN = 8
SUPPLY = AVDD1x = 3.3V + 100mV p-p
SUPPLY = AVDD1x = 3.3V + 100mV p-p
–20
–40
–40
–60
–60
–80
–80
–100
–120
–140
–100
–120
–140
INPUT FREQUENCY (Hz)
INPUT FREQUENCY (Hz)
Figure 80. CMRR vs. Input Frequency at 128 kSPS, High Resolution Mode
Figure 83. CMRR vs. Input Frequency at 32 kSPS, Low Power Mode
0
0
T
= 25°C
T = 25°C
A
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 1
GAIN = 2
GAIN = 4
GAIN = 8
A
–10
–20
–10
–20
SUPPLY = AVDD1x = 3.3V+100mVpp
SUPPLY = AVDD1x = 3.3V + 100mV p-p
–30
–30
–40
–40
–50
–50
–60
–60
–70
–70
–80
–80
–90
–90
–100
–110
–120
–130
–140
–150
–160
–100
–110
–120
–130
–140
–150
–160
INPUT FREQUENCY(Hz)
INPUT FREQUENCY(Hz)
Figure 81. AC PSRR vs. Input Frequency at 128 kSPS, High Resolution
Mode
Figure 84. AC PSRR vs. Input Frequency at 32 kSPS, Low Power Mode
10
0
GAIN = 1
GAIN = 1
0
–10
GAIN = 2
GAIN = 2
GAIN = 4
GAIN = 8
GAIN = 4
GAIN = 8
–10
–20
–20
–30
–40
–30
–40
–50
–50
–60
–60
–70
–70
–80
–80
–90
–90
–100
–110
–120
–100
–110
–120
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 82. Filter Profiles at 64 kSPS, High Resolution Mode
Figure 85. Filter Profiles at 16 kSPS, Low Power Mode
Rev. 0 | Page 29 of 98
AD7771
Data Sheet
20
18
16
14
12
10
8
6
5
4
3
2
1
0
AVDD1x
AVDD2x
AVDD4
IOVDD
AVDD1x
AVDD2x
AVDD4
IOVDD
6
4
2
0
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Figure 86. Supply Current vs. Supply Voltage, High Resolution Mode
Figure 89. Supply Current vs. Supply Voltage, Low Power Mode
30
7
AVDD1x
AVDD2x
AVDD4
AVDD1x
AVDD2x
AVDD4
IOVDD
6
5
4
3
2
1
0
25
IOVDD
20
15
10
5
0
–40
–20
0
20
40
60
80
100
120
–40
–20
0
20
40
60
80
100
120
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 87. Supply Current vs. Temperature High Resolution Mode
Figure 90. Supply Current vs. Temperature Low Power Mode
800
300
REF1–
REF1+
REF2–
REF2+
200
100
600
400
0
200
–100
–200
–300
–400
–500
–600
0
–200
–400
–600
–800
REF1–
REF1+
REF2–
REF2+
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 88. Reference Input Current vs. Temperature, High Resolution Mode
Figure 91. Reference Input Current vs. Temperature, Low Power Mode
Rev. 0 | Page 30 of 98
Data Sheet
AD7771
80
70
60
50
40
30
500
450
400
350
300
250
200
150
100
50
AVDD1x
AVDD2x
AVDD4
IOVDD
20
AVDD1x
AVDD2x
10
AVDD4
IOVDD
0
1.8
0
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
–60 –40 –20
0
20
40
60
80
100 120 140
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
Figure 92. Shutdown Supply Current vs. Supply Voltage
Figure 95. Shutdown Supply Current vs. Temperature
60
50
40
30
20
10
0
20
18
16
14
12
10
8
AVDD1x
AVDD2x
AVDD4
IOVDD
AVDD1x
AVDD2x
AVDD4
IOVDD
6
4
2
0
2.0
2.0
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
2.2
2.4
2.6
2.8
3.0
3.2
3.4
3.6
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Figure 93. Power Consumption per Channel vs. Supply Voltage,
High Resolution Mode
Figure 96. Power Consumption per Channel vs. Supply Voltage,
Low Power Mode
90
25
AVDD1x
AVDD1x
AVDD2x
AVDD4
AVDD2x
AVDD4
IOVDD
80
70
60
50
40
30
20
10
0
IOVDD
20
15
10
5
0
–40
–40
–20
0
20
40
60
80
100
120
–20
0
20
40
60
80
100
120
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 94. Power Dissipation vs. Temperature, High Resolution Mode
Figure 97. Power Dissipation vs. Temperature, Low Power Mode
Rev. 0 | Page 31 of 98
AD7771
Data Sheet
TERMINOLOGY
Common-Mode Rejection Ratio (CMRR)
Gain Error
CMRR is the ratio of the power in the ADC output at full-scale
frequency, f, to the power of a 100 mV p-p sine wave applied to
the common-mode voltage of AINx+ and AINx− at frequency, fS.
The first transition (from 100 … 000 to 100 … 001) occurs at a
level ½ LSB above nominal negative full scale (−2.49999 V for the
2.5 V range). The last transition (from 011 … 110 to 011 …
111) occurs for an analog voltage 1½ LSB below the nominal
full scale (2.49999 V for the 2.5 V range). The gain error is the
deviation of the difference between the actual level of the last
transition and the actual level of the first transition from the
difference between the ideal levels.
CMRR (dB) = 10 log(Pf/PfS)
where:
Pf is the power at frequency, f, in the ADC output.
PfS is the power at frequency, fS, in the ADC output.
Differential Nonlinearity (DNL) Error
Gain Error Drift
In an ideal ADC, code transitions are 1 LSB apart. Differential
nonlinearity is the maximum deviation from this ideal value.
DNL error is often specified in terms of resolution for which no
missing codes are guaranteed.
Gain error drift is the ratio of the gain error change due to a
temperature change of 1°C and the full-scale range (2N). It is
expressed in ppm/°C.
Least Significant Bit (LSB)
Integral Nonlinearity (INL) Error
The least significant bit, or LSB, is the smallest increment that
can be represented by a converter. For a fully differential input
ADC with N bits of resolution, the LSB expressed in volts is
Integral nonlinearity error refers to the deviation of each individual
code from a line drawn from negative full scale through positive
full scale. The point used as negative full scale occurs ½ LSB before
the first code transition. Positive full scale is a level 1½ LSB beyond
the last code transition. The deviation is measured from the middle
of each code to the true straight line.
2×VREF
LSB (V) =
2N
The LSB referred to the input is
Dynamic Range
2×VREF
Dynamic range is the ratio of the rms value of the full-scale
input signal to the rms noise measured for an input. The value
for dynamic range is expressed in decibels.
PGAGAIN
LSB (VIN) =
2N
Power Supply Rejection Ratio (PSRR)
Channel to Channel Isolation
Variations in power supply affect the full-scale transition but not
the linearity of the converter. PSRR is the maximum change in the
full-scale transition point due to a change in the power supply
voltage from the nominal value.
Channel to channel isolation is a measure of the level of
crosstalk between channels. It is measured by applying a full-scale
frequency sweep sine wave signal to all seven unselected input
channels and determining how much that signal is attenuated in
the selected channel. The value is given for worst case scenarios
across all eight channels of the AD7771.
Signal-to-Noise Ratio (SNR)
SNR is the ratio of the rms value of the actual input signal to
the rms sum of all other spectral components below the Nyquist
frequency, excluding harmonics and dc. The value for SNR is
expressed in decibels.
Intermodulation Distortion
With inputs consisting of sine waves at two frequencies, fA and
fB, any active device with nonlinearities creates distortion
products at the sum and difference frequencies of mfA and nfB,
where m, n = 0,1, 2, 3, and so on. Intermodulation distortion
terms are those for which neither m nor n are equal to 0. For
example, the second-order terms include (fA + fB) and (fA − fB and
the third-order terms include (2fA + fB), (2fA − fB), (fA + 2fB), and
(fA − 2fB). The AD7771 is tested using the CCIF standard, where
two input frequencies near the top end of the input bandwidth
are used. In this case, the second-order terms are usually distanced
in frequency from the original sine waves, and the third-order terms
are usually at a frequency close to the input frequencies. As a result,
the second-order and third-order terms are specified separately.
The calculation of the intermodulation distortion is per the THD
specification, where it is the ratio of the rms sum of the individual
distortion products to the rms amplitude of the sum of the
fundamentals, expressed in decibels.
Signal-to-(Noise + Distortion) Ratio (SINAD)
SINAD is the ratio of the rms value of the actual input signal to
the rms sum of all other spectral components below the Nyquist
frequency, including harmonics but excluding dc. The value for
SINAD is expressed in decibels.
Spurious-Free Dynamic Range (SFDR)
SFDR is the difference, in decibels, between the rms amplitude of
the input signal and the peak spurious signal including harmonics.
Total Harmonic Distortion (THD)
THD is the ratio of the rms sum of the first five harmonic
components to the rms value of a full-scale input signal and
is expressed in decibels.
Rev. 0 | Page 32 of 98
Data Sheet
AD7771
Offset Error
Offset Error Drift
Offset error is the difference between the ideal midscale input
voltage (0 V) and the actual voltage producing the midscale
output code.
Offset error drift is the ratio of the offset error change due to a
temperature change of 1°C and the full-scale code range (2N). It
is expressed in µV/°C.
Rev. 0 | Page 33 of 98
AD7771
Data Sheet
THEORY OF OPERATION
The AD7771 is an 8-channel, simultaneously sampling, low
noise, 24-bit Σ-Δ ADC with integrated digital filtering per
channel and SRC.
QUANTIZATION NOISE
fCLKIN/2
The AD7771 offers two operation modes: high resolution mode,
which offers up to 128 kSPS, and low power mode, which offers
up to 32 kSPS.
BAND OF INTEREST
Figure 98. Σ-Δ ADC Operation, Reduction of Noise Energy Contained in the
Band of Interest (Linear Scale X-Axis)
The AD7771 employs a Σ-Δ conversion technique to convert
the analog input signal into an equivalent digital word. The
overview of the Σ-Δ technique is that the modulator samples
the input waveform and outputs an equivalent digital word at
NOISE SHAPING
fCLKIN/2
the input clock frequency, fCLKIN
.
BAND OF INTEREST
Figure 99. Σ-Δ ADC Operation, Majority of Noise Energy Shifted Out of the
Band of Interest (Linear Scale X-Axis)
Due to the high oversampling rate, this technique spreads the
quantization noise from 0 Hz to fCLKIN/2 (in the case of the AD7771,
fCLKIN relates to the external clock); therefore, the noise energy
contained in the band of interest is reduced (see Figure 98). To
further reduce the quantization noise, a high order modulator is
employed to shape the noise spectrum so that most of the noise
energy is shifted out of the band of interest (see Figure 99). The
digital filter that follows the modulator removes the large out of
band quantization noise (see Figure 100).
DIGITAL FILTER CUTOFF FREQUENCY
fCLKIN/2
BAND OF INTEREST
Figure 100. Σ-Δ ADC Operation, Removal of Noise Energy from the Band of
Interest (Linear Scale X-Axis)
The Σ-Δ ADC starts the conversions of the input signal after the
supplies generated by the internal LDO regulators become stable.
An external signal is not required to generate the conversions.
For more information on basic and advanced concepts of Σ-Δ
ADCs, see the MT-022 Tutorial and MT-023 Tutorial.
Digital filtering has certain advantages over analog filtering.
Because digital filtering occurs after the analog-to-digital
conversion process, it can remove noise injected during the
conversion. Analog filtering cannot remove noise injected
during conversion.
ANALOG INPUTS
The AD7771 can be operated in bipolar or unipolar modes and
accepts true differential, pseudo differential, and single-ended
input signals, as shown in Figure 101 through Figure 104.
Table 10 summarizes the maximum differential input signal and
dynamic range for the different input modes.
Table 10. Input Signal Modes
Input Signal Mode PGA Gain
Maximum Differential Signal
Maximum Peak-to-Peak Signal
2 × VREF/PGAGAIN
2 × VREF/PGAGAIN
True differential
Pseudo differential
Single-ended
All gains
All gains
All gains
(VREF/PGAGAIN
(VREF/PGAGAIN
VREF/PGAGAIN
)
)
VREF/PGAGAIN
Rev. 0 | Page 34 of 98
Data Sheet
AD7771
1.6500
1.2375
BIPOLAR OR UNIPOLAR
TRUE DIFFERENTIAL
PSEUDO DIFFERENTIAL
AVDD1x – 0.1V
0.8250
0.4125
(AVDD1x + AVSSx)/2
–0.4125
AINx+
AINx+
VCM
/PGA
GAIN
V
REF
–0.8250
V
= 2.5V
REF
–1.2375
AVDD1x = 1.65V
AVSSx = –1.65V
–1.6500
1
2
4
8
AVSSx + 0.1V
PGA GAIN
Figure 101. Σ-Δ ADC Input Signal Configuration, True Differential
BIPOLAR OR UNIPOLAR
Figure 105. Maximum Common-Mode Voltage Range for a Maximum
Differential Input Signal
The AD7771 provides a common-mode voltage pin (AVDD1x +
AVSSx)/2), VCM, for the single-supply, pseudo differential, or true
differential input configurations.
AVDD1x – 0.1V
V
/PGA
GAIN
REF
TRANSFER FUNCTION
AINx+
AINx+
VCM
The AD7771 can operate with up to a 3.6 V reference, typical
at 2.5 V, and converts the differential voltage between the analog
inputs (AINx+ and AINx−) into a digital output. The ADC
converts the voltage difference between the analog input pins
(AINx+ − AINx−) into a digital code on the output. The 24-bit
conversion result is in MSB first, twos complement format, as
shown in Table 11 and Figure 106.
AVSSx + 0.1V
Figure 102. Σ-Δ ADC Input Signal Configuration, Pseudo Differential
BIPOLAR
Table 11. Output Codes and Ideal Input Voltages for PGA = 1×
Analog Input
((AINx+) − (AINx−)), Twos Complement
Digital Output Code,
V
/PGA
GAIN
REF
AINx+
AINx+
Condition
FS − 1 LSB
Midscale + 1 LSB
Midscale
Midscale − 1 LSB
−FS + 1 LSB
−FS
VREF = 2.5 V
+2.499999702 V
+298 nV
0 V
−298 nV
(Hexadecimal)
0x7FFFFF
0x000001
0x000000
0xFFFFFF
AVSSx + 0.1V
−2.499999702 V
−2.5 V
0x800001
0x800000
Figure 103. Σ-Δ ADC Input Signal Configuration, Single-Ended Bipolar
UNIPOLAR
011 ... 111
011 ... 110
011 ... 101
V
/PGA
GAIN
REF
AINx+
AINx+
+ 0.1V
100 ... 010
100 ... 001
Figure 104. Σ-Δ ADC Input Signal Configuration, Single-Ended Unipolar
100 ... 000
The common mode input signal is not limited, but keep the
absolute input signal voltage on any AINx pin between
AVSSx + 100 mV and AVDD1x − 100 mV; otherwise, the input
signal linearity degrades and, if the signal voltage exceeds the
absolute maximum signal rating, damages the device.
–FSR
–FSR + 1LSB
+FSR – 1LSB
–FSR + 0.5LSB
+FSR – 1.5LSB
ANALOG INPUT
Figure 106. Transfer Function
Figure 105 shows the maximum and minimum voltage common-
mode range at different PGA gains for a maximum differential
input voltage.
Rev. 0 | Page 35 of 98
AD7771
Data Sheet
MCLK
START SYNC_OUT
SYNC_IN
RESET
PGA
GAIN 1, 2, 4, 8
GAIN
SCALING
AND
DIGITAL
FILTER
SINC3/
SINC5
DRDY
DOUTx
DCLK
AINx+
AINx–
Σ-Δ
MODULATOR
CONVERSION
DATA INTERFACE
OFFSET
CORRECTION
SRC
ESD
PROTECTION
SIGNAL CHAIN FOR CHANNEL x
CONTROL BLOCK
FORMAT0
AND
FORMAT1
CONTROL
OPTION
PIN OR SPI
PIN CONTROL
SPI CONTROL
MODE0 TO MODE3
CS SCLK SDO SDI
Figure 107. Top Level Core Signal Chain
for the maximum common-mode voltage at maximum
differential input signals.
CORE SIGNAL CHAIN
Each Σ-Δ ADC channel on the AD7771 has an identical signal path
from the analog input pins to the digital output pins. Figure 107
shows a top level implementation of this signal chain. Prior to
each Σ-Δ ADC, a PGA maps sensor outputs into the ADC inputs,
providing low input current in dc ( 8 nA, input current, and
2 nA differential input current for high resolution mode), an
8 pF input capacitance in ac, and configurable gains of 1, 2, 4,
and 8. See the AN-1392 Application Note for more information.
Each ADC channel has its own Σ-Δ modulator, which oversamples
the analog input and passes the digital representation to the
digital filter block. The data is filtered, scaled for gain and
offset, and is then output on the data interface.
INTERNAL REFERENCE AND REFERENCE BUFFERS
The AD7771 integrates a 2.5 V, 10 ppm/°C (typical), voltage
reference that is disabled at power-up. The buffered reference is
available at Pin 49 and offers up to 10 mA of continuous current.
A 100 nF capacitor is required if the reference is enabled.
In applications where a low noise reference is required, it is
recommended to add a low-pass filter (LPF) with a cutoff
frequency (fCUTOFF) below 10 Hz to the REF_OUT pin. Connect
the output of this filter to REFx+, and connect AVSSx to REFx−.
In this scenario, configure the Σ-Δ reference as external. An
example of performance with and without the output filter is
shown in Figure 108.
To minimize power consumption, the channels can be
individually disabled.
115
V
= INTERNAL REFERENCE
REF
CAPACITIVE PGA
fCUTOFF = 10Hz
Each Σ-Δ ADC has a dedicated PGA, offering gain ranges of 1,
2, 4, and 8. This PGA reduces the need for an external input buffer
and allows the user to amplify small sensor signals to use the
full dynamic range of the AD7771.
105
95
The PGA maximizes the signal chain dynamic range for small
sensor output signals.
85
The AD7771 uses chopping of the PGA to minimize offset and
offset drift in the input amplifier, reducing the 1/f noise as well.
For the AD7771, the chopping frequency is set to 128 kHz for
high resolution mode, and 32 kHz for low power mode (see the
AN-1392 Application Note for more information). The chopping
tone is rejected by the sinc3 or sinc5 filters.
75
0.05
0.50
1.00
2.00
2.50
DIFFERENTIAL INPUT VOLTAGE (V)
Figure 108. SNR Adding External LPF with VREF = Internal Reference and
CUTOFF = 10 Hz
f
To minimize intermodulation effects that may cause an image
in the band of interest, it is recommended to limit the input
signal bandwidth to 2/3 of the chop frequency.
The AD7771 can be used with an external reference connected
between the REFx+ and REFx− pins. Recommended reference
voltage sources for the AD7771 include the ADR441 and ADR4525
family of low noise, high accuracy voltage references.
The capacitive PGA common-mode voltage does not depend on
the gain, and can be any value as long as the input signal voltage is
within AVSSx + 100 mV to AVDD1x − 100 mV. See Figure 105
Rev. 0 | Page 36 of 98
Data Sheet
AD7771
DCLK DIVIDER
1, 2, 4, 8, 16, 32, 64, 128
MCLK DIVIDER
HIGH RESOLUTION MODE: MCLK/4
LOW POWER MODE: MCLK/8
MCLK
MOD_MCLK
DCLKx
DRDY
AINx+
AINx–
DATA
INTERFACE
CONTROL
ADC
MODULATOR
SINC
FILTER
PGA
DOUT3
TO
DOUT0
DEC RATES = ×16, ×32, ×64, ×128, ×256, ×512, ×1024, ×2048, ×4095.99
Figure 109. Clock Generation on the AD7771
The reference buffers can be operated in three different modes:
buffer enabled mode, buffer bypassed mode, and buffer
precharged mode.
CLOCKING AND SAMPLING
The AD7771 includes eight Σ-Δ ADC cores. Each ADC receives
the same master clock signal. The AD7771 requires a maximum
external MCLK frequency of 8192 kHz for high resolution mode
and 4096 kHz for low power mode. The MCLK is internally
divided by 4 in high performance mode and by 8 in low power
mode to produce the modulator MCLK (MOD_MCLK) signal
used as the modulator sampling clock for the ADCs. The MCLK
can be decreased to accommodate lower ODRs if the minimum
ODR selected by the sinc3 filter is not low enough. If the external
clock is lower than 250 kHz, set the CLK_QUAL_DIS bit (in
SPI control mode only).
In buffer enabled mode, the buffer is fully enabled, minimizing
the current requirements from the external references. Note that
the buffer output voltage headroom is 100 mV from the rails.
In buffer bypassed mode, the external reference is directly
connected to the ADC reference capacitors; the reference must
provide enough current to correctly charge the internal ADC
reference capacitors. In this mode of operation, a degradation in
crosstalk is expected because the ADC channels are not isolated
from each other.
The AD7771 integrates an internal oscillator clock that initializes
the internal registers at power-up. The CLK_SEL pin defines the
external clock used after initialization (see Table 12).
Buffer precharged (pre-Q) mode is the default operation mode.
It is a hybrid mode where the internal reference buffers are
connected during the initial acquisition time to precharge the
internal ADC reference capacitors. During the final phase of the
acquisition, the reference is connected directly to the ADC
capacitors. This mode has some benefits compared to the buffer
enabled and buffer bypassed modes. In buffer pre-Q mode, the
reference current requirements are minimized compared to
buffer bypassed mode and the noise contribution from the
internal reference buffers is removed (compared to buffer
enabled mode).
Table 12. Clock Sources
CLK_SEL State Clock Source Connection
0
CMOS
Input to XTAL2/MCLK, IOVDD
logic level. XTAL1 must be
tied to DGND.
1
Crystal
Connected between XTAL1
and XTAL2/MCLK.
The MCLK signal generates the DCLK output signal, which in
turn clocks the Σ-Δ conversion data from the AD7771, as
shown in Figure 109.
In buffer pre-Q mode, the headroom/footroom of the buffer
reference is not applicable because the reference sets the final
voltage in the ADC reference capacitors.
DIGITAL RESET AND SYNCHRONIZATION PINS
INTEGRATED LDOs
An external pulse in the
pin generates the internal
SYNC_IN
The AD7771 has three internal LDOs to regulate the internal
supplies: two LDOs for the analog block and one LDO for the
digital core. The internal LDOs requires an external 1 µF
decoupling capacitor on the DREGCAP, AREG1CAP, and
the AREG2CAP pins. The LDO slew rate may be low because
it depends on the main supply slew rate; therefore, a hardware
reset of the digital block; this pulse does not affect the data
programmed in the internal registers. A pulse in this pin is
required in two cases as follows:
•
After updating one or more registers directly related to the
sinc filter (power mode, offset, gain, phase compensation,
and sinc filter).
RESET
reset generated by pulsing the
pin at power-up is required
•
To synchronize multiple devices.
to guarantee that the digital block initializes correctly.
SYNC_IN
The pulse in the
pin must be synchronous with MCLK.
Rev. 0 | Page 37 of 98
AD7771
Data Sheet
There are two different ways to achieve a synchronous pulse if
the controller/processor cannot generate it as follows:
The digital sinc3 filter implements three main notches, one at
the maximum ODR (128 kHz or 32 kHz, depending on the
power mode) and another two at the ODR frequency selected to
stop noise aliasing into the pass band. The sinc5 filter implements
five notches, one at the maximum ODR (128 kHz or 32 kHz,
depending on the power mode) and another four at the ODR
frequency selected to stop noise aliasing into the pass band.
It is recommended to select the sinc5 digital filter for output
data rates higher than 24 kSPS.
•
Applying an asynchronous pulse on the
pin, which
START
is then internally synchronized with the external MCLK
clock, and the resulting synchronous signal is output on
SYNC_OUT
Triggering the
the
pin.
SYNC_OUT
•
internally. When the AD7771
is configured in SPI control mode, toggling Bit 0 in the
GENERAL_USER_CONFIG_2 register generates a
Figure 111 and Figure 112 show the typical filter transfer
function for the high resolution and low power modes using a
decimation rate of 32 samples for the sinc3 and sinc5 filters.
SYNC_OUT
synchronous pulse that is output on the
pin.
SYNC_IN
SYNC_OUT
pins must be externally
The
and
0
connected if internal synchronization is used.
SINC3
SINC5
–10
If multiple AD7771 devices must be synchronized, the
–20
–30
–40
–50
–60
–70
–80
–90
–100
SYNC_OUT
pin of one device can be connected to multiple
devices. This synchronization method requires the use of a
common MCLK signal for all the AD7771 devices connected,
as shown in Figure 110.
If the
pin is not used, tie it to DGND.
START
ASYNCHRONOUS
PULSE
AD7771
START
SYNC_OUT
MCLK
SYNCHRONIZATION
0
32
64
96
128
160
192
224
256
LOGIC
FREQUENCY (MHz)
DIGITAL FILTER
Figure 111. Sinc3/Sinc5 Frequency Response in High Resoltuion Mode
0
SYNC_IN
SINC3
SINC5
–10
–20
–30
–40
–50
–60
–70
–80
–90
–100
IOVDD
AD7771
START
SYNC_OUT
MCLK
SYNCHRONIZATION
MCLK
NC
LOGIC
DIGITAL FILTER
SYNC_IN
IOVDD
AD7771
0
8
16
24
32
40
48
56
64
START
FREQUENCY (MHz)
MCLK
SYNC_OUT
SYNCHRONIZATION
NC
LOGIC
Figure 112. Sinc3/Sinc5 Frequency Response in Low Power Mode
DIGITAL FILTER
The sample rate converter feature allows fine tuning of the
decimation rate, even for noninteger multiples of the decimation
rate. See the Sample Rate Converter (SRC) section for more
information on filter profiles for noninteger decimation rates.
SYNC_IN
Figure 110. Multiple AD7771 Devices Synchronization
SHUTDOWN MODE
DIGITAL FILTERING
The AD7771 can be placed in shutdown mode by pulling
AVDD2x to ground and connecting 1 MΩ resistance, pulled
low, to XTAL2/MCLK. In this mode, the average current
consumption is reduced to 1 mA, as shown in Figure 113.
The AD7771 offers low latency sinc3 and sinc5 filters. Most
precision Σ-Δ ADCs use sinc filters because the sinc filters offer
a low latency path for applications requiring low bandwidth
signals, for example, in control loops or where application
specific postprocessing is required. The digital filter adds notches
at multiples of the sampling frequency.
Rev. 0 | Page 38 of 98
Data Sheet
AD7771
1.0
I
PIN CONTROL MODE
AVDD1x
I
I
I
AVDD2x
AVDD4
IOVDD
In pin control mode, the AD7771 is configured at power-up
based on the level of the mode pins, MODE0, MODE1, MODE2,
and MODE3. These four pins set the following functions on the
AD7771: the mode of operation, the decimation rate/ODR, the
PGA gain, and the reference source, as shown in Table 14.
AVDDx = 3.3V
IOVDD = 3.3V
0.5
Due to the limited number of mode pins and the number of
options available, the PGA gain control is grouped into blocks
of 4, and the ODR is selected for the maximum value defined by
the decimation rate; ODR (kHz) = 2048/decimation for high
resolution mode, and ODR (kHz) = 512/decimation for low
power mode.
0
–0.5
–40
10
60
125
TEMPERATURE (°C)
Depending on the mode selected, the device is configured to
use an external or an internal reference.
Figure 113. Shutdown Current
CONTROLLING THE AD7771
The conversion data can be read back using the SPI or the data
output interface, as shown in Table 13. If the data output interface is
used to read back the data from the conversions, the number of
DOUTx lines enabled and the number of clocks required for
the Σ-Δ data transfer are determined by the logic level of the
CONVST_SAR, FORMAT0, and FORMAT1 pins. In this case,
the DCLK2, DCLK1, and DCLK0 pins select the Σ-Δ output
interface and control the DCLKx divide function, which is a
submultiple of MCLK, as shown in Table 15. The DCLKx divide
function sets the frequency of the data output interface DCLKx
signal. The DCLK minimum frequency depends on the
decimation rate and operation mode. See the Data Output
Interface section for more details about the minimum DCLKx
frequency.
The AD7771 can be controlled using either pin control mode or
SPI control mode.
Pin control mode allows the AD7771 to be hardwired to predefined
settings that offer a subset of the overall functionality of the
AD7771. In this mode, the SRC and diagnostic features or
extended errors source are not available.
Controlling the AD7771 over the SPI allows the user access to
the full monitoring, diagnostic, and Σ-Δ control functionality.
SPI control offers additional functionality such as offset, gain,
and phase correction per channel, in addition to access to the
flexible SRC to achieve a coherent sampling.
See Table 13 for more details about these different configurations.
All the pins that define the AD7771 configuration mode are
reevaluated each time the
pin is pulsed. The typical
SYNC_IN
connection diagram for pin control mode is shown in Figure 114.
Table 13. Format of the Data Interface
CONVST_SAR State
FORMAT1
FORMAT0
Control Mode
Data Output Mode
1
0
0
1
1
0
0
1
1
1
0
Pin
Pin
Pin
SPI
Pin
SPI output
SPI output
SPI output
Defined in Register 0x014
DOUT0, Channel 0 and Channel 1
DOUT1, Channel 2 and Channel 3
DOUT2, Channel 4 and Channel 5
DOUT3, Channel 6 and Channel 7
DOUT0, Channel 0 to Channel 3
DOUT1, Channel 4 to Channel 7
DOUT0, Channel 0 to Channel 7
Defined in Register 0x014
0
0
1
Pin
1
1
0
1
Pin
SPI
Rev. 0 | Page 39 of 98
AD7771
Data Sheet
Table 14. Pin Control Mode Options
Pin State
PGA Gain Channel
Decimation
Rate
Channel 0 to Channel 4 to
Reference
MODE3
MODE2
MODE1
MODE0
Power Mode
High resolution
High resolution
High resolution
High resolution
High resolution
High resolution
High resolution
High resolution
High resolution
High resolution
High resolution
High resolution
Low power
Channel 3
Channel 7
Source
External
External
External
External
External
External
External
External
External
Internal
Internal
Internal
External
External
External
External
Filter
Sinc5
Sinc5
Sinc5
Sinc5
Sinc5
Sinc5
Sinc5
Sinc5
Sinc5
Sinc5
Sinc5
Sinc5
Sinc5
Sinc5
Sinc3
Sinc3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
16
16
32
32
64
64
128
128
256
16
32
64
16
32
64
32
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
4
1
4
1
4
1
4
1
1
1
1
1
1
1
1
Low power
Low power
Low power
Table 15. DCLKx Selection for Pin Control Mode State
DCLK2/SCLK
DCLK1/SDI
DCLK0/SDO
MCLK Divider
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
1
2
4
8
16
32
64
128
Rev. 0 | Page 40 of 98
Data Sheet
AD7771
EXTERNAL
REFERENCE
AVDD 3.3V
AVDD3.3V
AVDD3.3V
IOVDD 2V TO 3.6V
AVSSx
REFx+
AVSSx
AVSSx
AVDD4
AVSSx
AVSSx
AVSSx
AVDD1x
REFx–
REF_OUT
AVDD2x AREGxCAP IOVDD DREGCAP
SYNC_IN
SYNC_OUT
START
VCM
VCM
BUFFER
BUFFER
AD7771
RESET
DRDY
AIN0+
AIN0–
PGA
PGA
DCLK
ADC
DOUT0
DOUT1
DOUT2
DOUT3
DATA
SERIAL
INTERFACE
SPI/SPORT
SLAVE
AIN7+
AIN7–
24-BIT
Σ-Δ
ADC
INTERFACE
SINC3/SINC5
FPGA
SRC
OR
DSP
CS
SCLK
SDO
SPI
CONTROL
INTERFACE
SPI
MASTER
INTERFACE
SDI
CLK_SEL
AVSSx
MODE3
TO
MODE0
XTAL1
XTAL2
CONVST_SAR
DCLK2
TO
DCLK0
FORMAT1
AND
FORMAT0
CLOCK
SOURCE
Figure 114. Pin Control Mode Connection Diagram with External Reference
AVDD 3.3V
AVDD3.3V
IOVDD 2V TO 3.6V
AVSSx
REFx+
AVSSx
REFx–
AVSSx
AVSSx
AVSSx
AVDD1x
REF_OUT
AVDD4 AVDD2x AREGxCAP IOVDD DREGCAP
SYNC_IN
SYNC_OUT
START
VCM
VCM
BUFFER
BUFFER
AD7771
RESET
DRDY
AIN0+
AIN0–
PGA
PGA
DCLK
ADC
DOUT0
DOUT1
DOUT2
DOUT3
DATA
SERIAL
INTERFACE
SPI/SPORT
SLAVE
AIN7+
AIN7–
24-BIT
Σ-Δ
ADC
INTERFACE
SINC3/SINC5
SRC
FPGA
OR
DSP
CS
SPI
CONTROL
INTERFACE
SCLK
SDO
SDI
SPI
MASTER
INTERFACE
DIAGNOSTIC
INPUTS
FULL BUFFER
AUXAIN+
AUXAIN–
12-BIT
SAR ADC
CLK_SEL
MUX
AVSSx
GPIO2
TO
GPIO0
CONVST_SAR
XTAL1
XTAL2
FORMAT1
FORMAT0
IOVDD
IOVDD
CLOCK
SOURCE
Figure 115. SPI Control Mode Connection Diagram with Internal Reference
Rev. 0 | Page 41 of 98
AD7771
Data Sheet
Then, an LSB of the offset register adjustment changes the digital
output by −4/3 × 0.75 = 1 LSB. Program the gain register as follows:
SPI CONTROL
The second option for control and monitoring the AD7771 is
via the SPI. This option allows access to the full functionality
on the AD7771, including access to the SAR converter, phase
synchronization, offset and gain adjustment, diagnostics, and
the SRC. To use the SPI control, set the FORMAT0 and
FORMAT1 pins to logic high.
•
•
•
CHx_GAIN_UPPER_BYTE = 0x40
CHx_GAIN_MID_BYTE = 0x00
CHx_GAIN_LOWER_BYTE = 0x00
SPI Control Functionality
Global Control Functions
In this mode, the SPI can also read the Σ-Δ conversation data by
setting the SPI_SLAVE_MODE_EN bit.
The following list details the global control functions of the
AD7771:
The typical connection diagram for SPI control mode is shown
in Figure 115.
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
High resolution and low power modes of operation
ODR: SRC
Sinc3 and sinc5 filters
VCM buffer power-down
Internal/external reference selection
Enable, pre-Q, or bypassed reference buffer modes
Internal reference power-down
SAR diagnostic mux
SAR power-down
GPIO write/read
SPI SAR conversion readback
SPI slave mode—read Σ-Δ results
SDO and DOUTx drive strength
DOUTx mode
Functionality Available in SPI Control Mode
SPI control of the AD7771 offers the super set of the functions and
diagnostics. The SPI Control Functionality section describes the
functionality and diagnostics offered when in SPI control mode.
Offset and Gain Correction
Offset and gain registers are available for system calibration.
The gain register is preprogrammed during final production for
a PGA gain of 1, but can be overwritten with a new value if
required.
The gain register is 24 bits long and is split across three registers,
CHx_GAIN_UPPER_BYTE, CHx_GAIN_MID_BYTE, and
CHx_GAIN_LOWER_BYTE, which set the gain on a per
channel basis.
DCLK division
Internal LDO bypassed
Cyclic redundancy check (CRC) protection: enabled or
disabled
The gain value is relative to 0x555555, which represents a gain of 1.
The offset register is 24 bits long and is spread across three byte
registers, CHx_OFFSET_UPPER_BYTE, CHx_OFFSET_MID_
BYTE, and CHx_OFFSET_LOWER_BYTE. The default value is
0x000000 at power-up. Program the offset as a twos complement,
signed 24-bit number. If the channel gain is set to its nominal
value of 0x555555, an LSB of offset register adjustment changes
the digital output by −4/3 LSBs.
Per Channel Functions
The following list details the per channel functions of the
AD7771:
•
•
•
•
•
•
•
•
PGA gain.
Σ-Δ channel power-down.
Phase delay: synchronization phase offset per channel.
Calibration of offset.
As an example of calibration, the offset measured is −200 LSB
(with both AINx pins connected to the same potential).
An offset adjustment of −150 LSB changes the digital output by
−150 × (−4/3) = 200 LSBs (gain value = 0x555555), representing
this number as two complement, 0xFFFFFF − 0x96 + 1 =
0xFFFF70. Program the offset register as follows:
Calibration of gain.
Σ-Δ input signal mux.
Channel error register.
PGA gain.
•
•
•
CHx_OFFSET_UPPER_BYTE = 0xFF
CHx_OFFSET_MID_BYTE = 0xFF
CHx_OFFSET_LOWER_BYTE = 0x70
Phase Adjustment
The AD7771 phase delay can be adjusted to compensate for phase
mismatches between channels due to sensors or signal channel
phase errors connected to the AD7771. Achieve phase adjustment
by programming the CHx_SYNC_OFFSET register. This
programming delays the synchronization signal by a certain
number of modulator clocks (MOD_MCLK) to individually
initiate the digital filter for each Σ-Δ ADC.
Note that the offset compensation is performed before the gain
compensation. The gain is programmed during final testing for
PGAGAIN = 1. The gain register values can be overwritten; however,
after a reset or power cycle, the gain register values revert to the
hard coded programmed factory setting.
If the gain required is 0.75 of the nominal value (0x555555), the
value that must be programmed is
The phase adjustment register is read during the pulse; conse-
quently, any further changes on the register have no effect unless a
pulse is generated (see the Digital Reset and Synchronization
0x555555 × 0.75 = 0x400000
Rev. 0 | Page 42 of 98
Data Sheet
AD7771
Pins section for more information on how to generate a pulse in
the pin).
Refer to the Sample Rate Converter (SRC) section for more
information.
The phase offset register is multiplied internally by a factor that
depends on the decimation rate, as shown in Table 16.
GPIOx Pins
If the AD7771 operates in SPI control mode, the mode pins
operate as GPIOx pins, as shown in Figure 116. The GPIOx pins
can be configured as inputs or outputs in any order.
Table 16. Phase Adjustment vs. Decimation Rate
Phase Adjustment Compensation
Decimation Rate
×1
×2
×4
×8
×16
≤255
≤511
≤1023
≤2047
GPIO0
GPIO1
REGISTER
MAP
≤4095
GPIO2
The maximum phase delay cannot be equal to or greater than
the decimation rate. If this is the case, the value changes
internally to the decimation rate value minus 1.
Figure 116. GPIOx Pin Functionality
As an example, the phase mismatch between Channel 0 and
Channel 1 is 5°, and the ODR is 5 kSPS in high resolution mode. In
this case, the decimation rate is 2048 kHz/5 kHz = 409.6, which
means that the offset register value is multiplied internally by 2.
Configuration control and readback of the GPIOx pins are set
via Bits[2:0] in the GPIO_CONFIG register (0 = input, 1 = output)
and the GPIO_DATA register. Among other uses, the GPIOs
can control an external mux connected to the auxiliary inputs of
the SAR ADC. Use this mux to verify the results on the Σ-Δ ADCs.
Assuming an input signal of 50 Hz, the number of MOD_
MCLK pulses required to sample a full period is 2048 kHz/
50 Hz = 40960 > 360°/40960 = 0.00878°.
In addition, the GPIOx pins can be used to externally trigger a
new decimation rate. Refer to the Sample Rate Converter (SRC)
section for more information about this functionality.
If a 5° delay is required, the number of MOD_MCLK delays
must be 569 (5°/0.00878°) because the offset register is multiplied
by 2; the final offset register value is 409.6/2 − 569/2, which
gives a negative value. In this case, if the offset value programmed
to the register is higher than 204 (for example, 210 × 2 = 420),
the value is internally changed to 408, resulting in a phase
compensation of 408 × 0.00878° = 3.58°.
Σ-Δ Reference Configuration
The AD7771 can operate with internal or external references. In
addition, for diagnostic purposes, the analog supply can be used
as a reference, as shown in Table 18. REFx−/REFx+ allow the
selection of a voltage reference where the REFx+ voltage is
lower than the voltage on the REFx− pin.
PGA Gain
The PGA gain can be selected individually by appropriately select-
ing Bits[7:6] in the CHx_CONFIG register, as shown in Table 17.
Table 18. Σ-Δ References
Setting for
ADC_MUX_CONFIG, Channel 0 to
Channel 4 to
Channel 7
Table 17. PGA Gain Settings via CHx_CONFIG
Bits[7:6]
Channel 3
CHx_CONFIG, Bits[7:6] Setting
PGA Gain Setting
00
01
10
11
REF1+/REF1−
Internal reference
AVDD1A/AVSS1A
REF1−/REF1+
REF2+/REF2−
00
01
10
11
×1
×2
×4
×8
Internal reference
AVDD1B/AVSS1B
REF2−/REF2+
Reference buffer operation is described in Table 19. The selected
reference and buffer operation mode affect all channels.
If the Σ-Δ reference is updated, it is recommended to apply a
pulse on the pin to remove invalid samples during
the transition of the reference.
SYNC_IN
If the Σ-Δ reference is updated, it is recommended to apply a
SYNC_IN
pulse on the
pin to remove invalid samples during
Decimation
the transition of the reference.
The decimation defines the sampling frequency as follows:
•
In high resolution mode, the sampling frequency = MCLK/
(4 × decimation)
•
In low power mode, the sampling frequency = MCLK/
(8 × decimation)
Rev. 0 | Page 43 of 98
AD7771
Data Sheet
Table 19. Reference Buffer Operation Modes
Reference Buffer
Operation Mode
REFx+
REFx−
Enabled
BUFFER_CONFIG_1, Bit 4 = 1; BUFFER_CONFIG_2, Bit 7 = 0 BUFFER_CONFIG_1, Bit 3 = 1; BUFFER_CONFIG_2, Bit 6 = 0
Precharged
Disabled
BUFFER_CONFIG_1, Bit 4 = 1; BUFFER_CONFIG_2, Bit 7 = 1
BUFFER_CONFIG_1, Bit 4 = 0
BUFFER_CONFIG_1, Bit 3 = 1; BUFFER_CONFIG_2, Bit 6 = 1
BUFFER_CONFIG_1, Bit 3 = 0
Table 20. Additional Disable Power-Down Blocks
Block
Register
Notes
VCM
GENERAL_USER_CONFIG_1, Bit 5
BUFFER_CONFIG_1, Bits[4:3]
GENERAL_USER_CONFIG_1, Bit 4
CH_DISABLE, Bits[7:0]
GENERAL_USER_CONFIG_1, Bit 3
GENERAL_USER_CONFIG_1, Bit 2
Enabled by default
Precharge mode by default
Disabled by default
All channels enabled
Disabled by default
Enabled by default
Reference Buffer
Internal Reference Buffer
Σ-Δ Channel
SAR
Internal Oscillator
Power Modes
DIGITAL SPI
The AD7771 offers different power modes to improve the
power efficiency, high resolution and low power mode, which
can be controlled via GENERAL_USER_CONFIG_1, Bit 6. To
further reduce the power, additional blocks can be disabled
independently, as described in Table 20.
The SPI serial interface on the AD7771 consists of four signals:
CS
SPI is shown in Figure 117.
, SDI, SCLK, and SDO. A typical connection diagram of the
DSP/FPGA
AD7771
CS
SYNC_IN
If the power mode changes, a pulse on the
required.
pin is
SCLK
SDI
Sinc3 and Sinc5 Filters
The AD7771 implements sinc3 and sinc5 digital filters. By
default, the device powers up with the sinc3 filter, but it can be
changed by setting GENERAL_USER_CONFIG_2, Bit 6. If the
SDO
Figure 117. SPI Control Interface—AD7771 is the SPI Slave, Digital Signal
Processor (DSP)/Field Programmable Gate Array (FPGA) is the Master
SYNC_IN
sinc filter is changed, a pulse in the
pin is required.
LDO Bypassing
The SPIs operates in Mode 0 and Mode 3, CPOL = 0, CPHA = 0
(Mode 0) or CPOL = 1, CPHA = 1 (Mode 3).
The internal LDOs can be individually bypassed and an external
supply can be applied directly to the AREG1CAP, AREG2CAP,
or DREGCAP pin. Table 21 shows the absolute minimum and
maximum supplies for these pins, as well as the associated
register used to bypass the regulator.
In pin control mode, the SDI can read back the Σ-Δ results,
depending on the level of the CONVST_SAR pin, as described in
Table 13.
In SPI control mode, the SPI transfers data into the on-chip
registers while the SDO pin reads back data from the on-chip
registers or reads the SAR or the Σ-Δ conversions results,
depending on the selected operation mode.
Table 21. LDO Bypassing
Supply
Min (V)
BUFFER_CONFIG_2,
Bits[2:0]1
LDO
Max (V)
1.9
1.9
AREG1CAP 1XX
AREG2CAP X1X
1.85
1.85
1.65
The SDO data source in SPI control mode is defined by the
GENERAL_USER_CONFIG_2 and GENERAL_USER_
CONFIG_3 registers, as described in Table 22.
DREGCAP
XX1
1.9
1 X means don’t care.
Table 22. SPI Operation Mode in SPI Control Mode
GENERAL_USER_ GENERAL_USER_
CONFIG_2, Bit 5
Setting
CONFIG_3, Bit 4
Setting1
Mode
0
0
1
0
1
X
Internal register
Σ-Δ data conversion
SAR conversion
1 X means don’t care.
Rev. 0 | Page 44 of 98
Data Sheet
AD7771
In SPI control mode, there are four different levels of input/
output (I/O) strength on the SDO pin that can be selected in
GENERAL_USER_CONFIG_2, Bits[4:3], as described in Table 23.
Enabling the SPI_CRC_TEST_EN bit results in a CRC checksum
W
being performed on all the R/ operations. When SPI_CRC_
TEST_EN is enabled, an 8-bit CRC word is appended to every
SPI transaction for SAR and register map operations. For more
information on Σ-Δ readback operations, see the CRC Header
section.
Table 23. SDO Strength
GENERAL_USER_CONFIG_2, Bits[4:3] Setting
Mode
00
01
10
11
Nominal
Strong
Weak
To ensure that the register write is successful, it is recommended to
read back the register and verify the checksum.
For CRC checksum calculations, the following polynomial is
always used: x8 + x2 + x + 1. See the SPI Control Mode Checksum
section for more information.
Extra strong
SCLK is the serial clock input for the device. All data transfers
(on either SDO or SDI) occur with respect to this SCLK signal.
SPI Read/Write Register Mode (SPI Control Mode)
The SPI can operate in multiples of eight bits. For example, in
SPI control mode, if the SDO pin is used to read back the data
from the internal register or the SAR ADC, the data frame is
16 bits wide (CRC disabled), as shown in Figure 118, or 24 bits
wide (CRC enabled), as shown in Figure 119. In this case, the
controller can generate one frame of 16 bits or 24 bits (with and
without the CRC enabled), or two or three frames of 8 bits (with
and without the CRC enabled). When the SDO pin reads back
the data from the Σ-Δ channels, 64 bits must be read back from
the controller (in this case, the controller can generate a frame
of 64 bits—either 2 × 32 bits, 4 × 16 bits, or 8 × 8 bits).
The AD7771 has on-board registers to configure and control
the device.
The registers have 7-bit addresses—the 7-bit register address on
the SDI line selects the register for the read/write function. The
W
7-bit register address follows the R/ bit in the SDI data. The
8 bits on the SDI line following the 7-bit register address are the
data to be written to the selected register if the SPI is a write
transfer. Data on the SDI line is clocked into the AD7771 on
the rising edge of SCLK, as shown in Figure 3.
The data on the SDO line during the SPI transfer contains the
8-bit 0010 0000 header: 8 bits of register data in the case of a read
SPI CRC—Checksum Protection (SPI Control Mode)
W
(R) operation, or 8 zeros in the case of a write ( ) operation.
The AD7771 has a checksum mode that improves SPI
With the CRC disabled, the basic data frame on the SDI line
during the transfer is 16 bits long, as shown in Figure 118.
When the CRC is enabled, a minimum frame length of 24 SCLK
periods are required on SPI transfers. The 24 bits of data on the
SDO line consist of an 8-bit header (0010 0000), 8 bits of data, and
an 8-bit CRC (see Figure 119).
robustness in SPI control mode. Using the checksum ensures
that only valid data is written to a register and allows data read
from the device to be validated. The SPI CRC can be enabled by
setting the SPI_CRC_TEST_EN bit. If an error occurs during a
register write, the SPI_CRC_ERR is set in the error register.
CS
SCLK
SDI
R/W A6
A5
1
A4
0
A3
0
A2
0
A1
0
A0
0
D7
R7
D6
R6
D5
R5
D4
R4
D3
R3
D2
R2
D1
R1
D0
R0
SDO
0
0
Figure 118. 16-Bit SPI Transfer—CRC Disabled
CS
SCLK
SDI
ICRC7 ICRC6 ICRC5 ICRC4 ICRC3 ICRC2 ICRC1 ICRC0
R/W A6
A5
1
A4
0
A3
0
A2
0
A1
A0
0
D7
R7
D6
R6
D5
R5
D4
R4
D3
R3
D2
R2
D1
R1
D0
R0
SDO
ICRC7 ICRC6 ICRC5 ICRC4 ICRC3 ICRC2 ICRC1 ICRC0
0
0
0
Figure 119. 24-Bit SPI Transfer—CRC Enabled
Rev. 0 | Page 45 of 98
AD7771
Data Sheet
SPI SAR Diagnostic Mode (SPI Control Mode)
to the device, which is ignored because the SDO pin shifts out
the content of the SAR ADC.
Setting Bit 5 in the GENERAL_USER_CONFIG_2 register
configures the SDO line to shift out data from the SAR ADC
conversions, as described in Table 22.
If consecutive conversions are performed in the SAR ADC, read
back the result from the previous conversion before a new
conversion is generated. Otherwise, the results are corrupted.
In SAR mode, the AD7771 internal registers can be written to,
but any readback command is ignored because the SDO data
frame is dedicated to shift out the conversion results from the
SAR ADC.
Σ-Δ Data, ADC Mode
In pin control mode, the SPI can be used to read back the Σ-Δ
conversions as described in Table 13. In SPI control mode, the
SPI reads back the Σ-Δ conversions by setting GENERAL_USER_
CONFIG_3, Bit 4, as described in Table 22; in this mode, the
AD7771 internal register can be written to, but any readback
command is ignored because the SDO data frame is dedicated to
shifting out the conversion results from the Σ-Δ ADCs. To
avoid unwanted writes to the internal register, it is recommended
to send a readback command, for example, 0x8000, to the device,
which is ignored because the SDO pin shifts out the content of
the Σ-Δ ADC.
To exit this mode of operation, reset Bit 5 in the GENERAL_
USER_CONFIG_2 register.
The data on the SDO line during the SPI transfer contains a
4-bit 0010 header and the 12-bit SAR conversion result if the
CRC is disabled.
When the CRC is enabled, a minimum frame length of 24 SCLK
periods is required on SPI transfers. The 24 bits of data on the
SDO line consist of a 4-bit header (0010), the 12-bit data, and
an 8-bit CRC, as shown in Figure 120.
The SDO pin data can be read back in any multiple of 8 bits, for
example, as 64 bits, 2 × 32 bits, 4 × 16 bits, or 8 × 8 bits.
Per the SPI read/write register mode (see the SPI Read/Write
Register Mode section), the SDI line contains the R/ bit, a 7-bit
register address, the 8-bit data, and an 8-bit CRC (if enabled).
To avoid unwanted writes to the internal register while the SAR
conversions are read back through the SDO line, it is recom-
mended to send a readback command, for example, 0x8000,
W
SPI Software Reset
Keeping the SDI pin high during 64 consecutives clocks
generates a software reset.
CS
SCLK
ICRC7 ICRC6 ICRC5 ICRC4 ICRC3 ICRC2 ICRC1 ICRC0
SDI
R/W A6
A5
1
A4
0
A3
A2
A1
A0
D7
D6
D5
D4
D3
D2
D1
D0
SAR SAR SAR SAR SAR SAR SAR SAR SAR SAR SAR SAR
11
SDO
ICRC7 ICRC6 ICRC5 ICRC4 ICRC3 ICRC2 ICRC1 ICRC0
0
0
10
9
8
7
6
5
4
3
2
1
0
Figure 120. SAR ADC/Diagnostic Mode—CRC Enabled
Rev. 0 | Page 46 of 98
Data Sheet
AD7771
RMS NOISE AND RESOLUTION
Table 24 through Table 27 show the dynamic range (DR), rms
noise (RTI), effective number of bits (ENOB), and effective
resolution (ER) of the AD7771 for various output data rates and
gain settings. The numbers given are for the bipolar input range
with an external 2.5 V reference. These numbers are typical and
are generated with a differential input voltage of 0 V when the
ADC is continuously converting on a single channel.
It is important to note that the effective resolution is calculated
using the rms noise; 16,384 consecutives samples were used to
calculate the rms noise.
Effective Resolution = log2(Input Range/RMS Noise)
ENOB = (DR − 1.78)/6
HIGH RESOLUTION MODE
Table 24. DR and RTI for High Resolution Mode
Gain = 1
Gain = 2
RTI
Gain = 4
RTI
Gain = 8
RTI
Sinc
Filter
Decimation
Rate
Output Data
Rate (SPS)
f−3 dB
(Hz)
DR
(dB)
RTI
DR
DR
DR
(µV rms)
(dB)
(µV rms)
(dB)
(µV rms)
(dB)
(µV rms)
Sinc5
16
32
64
256
128
256
512
1024
128,000
64,000
32,000
8,000
26542.34
13403.14
6833.54
1906.34
4878.83
2756.43
1695.23
899.33
95.1
31.32
14.31
7.90
3.34
9.01
4.32
2.86
1.39
91.7
98.5
22.68
10.30
4.85
1.84
4.88
2.31
1.51
0.73
87.1
94.4
19.39
8.41
3.65
1.16
2.99
1.52
0.96
0.47
82.0
89.7
96.9
107.9
99.6
105.5
109.5
115.7
17.11
7.37
3.14
0.91
2.26
1.19
0.75
0.36
101.8
107.1
114.4
105.7
112.1
115.8
122.0
105.3
113.8
105.2
111.5
115.6
121.6
101.5
111.6
103.2
109.3
113.5
119.6
Sinc3
16,000
8,000
4,000
1,000
Table 25. ENOB and ER for High Resolution Mode
Gain = 1
Gain = 2
Gain = 4
Gain = 8
Sinc
Filter
Decimation
Rate
Output Data
Rate (SPS)
f−3 dB
(Hz)
ENOB
(Bits)
ER
(Bits)
ENOB
(Bits)
ER
(Bits)
ENOB
(Bits)
ER
(Bits)
ENOB
(Bits)
ER
(Bits)
Sinc5
16
32
64
256
128
256
512
1024
128,000
64,000
32,000
8,000
26542.34
13403.14
6833.54
1906.34
4878.83
2756.43
1695.23
899.33
15.5
16.6
17.5
18.7
17.3
18.3
18.9
20.0
17.3
18.4
19.3
20.5
19.1
20.1
20.7
21.8
14.9
16.1
17.2
18.6
17.2
18.2
18.9
19.9
17.8
18.9
20.0
21.4
20.0
21.0
21.7
22.7
14.2
15.4
16.6
18.2
16.9
17.9
18.6
19.6
18.0
19.2
20.4
22.0
20.7
21.6
22.3
23.3
13.3
14.6
15.8
17.6
16.3
17.2
17.9
18.9
18.2
19.4
20.6
22.4
21.1
22.0
22.7
23.7
Sinc3
16,000
8,000
4,000
1,000
Rev. 0 | Page 47 of 98
AD7771
Data Sheet
LOW POWER MODE
Table 26. DR and RTI for Low Power Mode
Gain = 1
RTI
Gain = 2
RTI
Gain = 4
RTI
Gain = 8
Sinc
Filter
Decimation
Rate
Output Data
Rate (SPS)
f−3 dB
(Hz)
DR
(dB)
DR
(dB)
DR
(dB)
DR
(dB)
RTI
(µV rms)
(µV rms)
(µV rms)
(µV rms)
Sinc5
16
32
64
512
64
128
256
1024
32,000
16,000
8,000
1,000
8,000
4,000
2,000
500
6833.54
3548.74
1906.34
469.24
94.3
34.2
15.7
83.3
25.2
29.86
9.47
4.62
2.1
90.9
97.8
25.04
11.22
5.18
86.5
93.6
20.5
9.0
4.03
8.41
8.9
3.21
1.57
0.7
81.3
87.9
96.1
110.7
90.8
98.7
104.8
112.5
19.43
8.39
3.46
0.67
6.11
2.51
1.27
0.54
100.9
106.7
117.1
95.5
105.4
111.7
118.6
104.6
116.8
95.0
105.1
111.2
118.2
100.6
114.4
93.7
102.7
108.9
116.2
1.29
Sinc3
2756.43
1695.23
1164.63
766.68
15.26
4.95
2.41
1.07
Table 27. ENOB and ER for Low Power Mode
Gain = 1
Gain = 2
Gain = 4
Gain = 8
Sinc
Filter
Decimation
Rate
Output Data
Rate (SPS)
f−3 dB
(Hz)
ENOB
ER
(Bits)
ENOB
(Bits)
ER
(Bits)
ENOB
(Bits)
ER
(Bits)
ENOB
ER
(Bits
(Bits)
15.4
16.5
17.4
19.2
15.6
17.2
18.3
19.4
(Bits)
13.2
14.3
15.7
18.1
14.8
16.1
17.1
18.4
Sinc5
16
32
64
512
64
128
256
1024
32,000
16,000
8000
1000
8,000
4,000
2,000
500
6833.54
3548.74
1906.34
469.24
17.2
18.3
15.9
17.6
17.4
19.0
20.0
21.2
14.8
16.0
17.1
19.1
15.5
17.2
18.2
19.3
17.6
18.8
19.9
21.9
18.3
19.9
21.0
22.2
14.1
15.3
16.4
18.7
15.3
16.8
17.8
19.0
17.9
19.1
20.2
19.2
19.1
20.6
21.6
22.8
18.0
19.2
20.5
22.8
19.6
20.9
21.9
23.1
Sinc3
2756.43
1695.23
1164.63
766.68
Rev. 0 | Page 48 of 98
Data Sheet
AD7771
DIAGNOSTICS AND MONITORING
the CMOS clock. In SPI control mode, if an error occurs in the
handover, the EXT_MCLK_SWITCH_ERR bit is set in the
general error register, GEN_ERR_REG_2.
SELF DIAGNOSTICS ERROR
The AD7771 includes self diagnostic features to guarantee the
correct operation. If an error is detected, the ALERT pin (Pin 18
when using pin control mode or Pin 16 when using SPI control
mode) is pulled high to generate an external interruption to the
controller. In addition, the header of the Σ-Δ output data
contains an alert bit that informs the controller of a chip error
(see the ADC Conversion Output—Header and Data section).
If EXT_MCLK_SWITCH_ERR is set, this means that the device
is operating using the internal oscillator.
To use a slow external clock (<265 kHz), set the CLK_QUAL_
DIS bit. Setting this bit also clears the error bit.
If the external clock is between 132 kHz and 265 kHz, depending
on the internal synchronization between the internal oscillator
and the external clock, the error may not trigger. However, it is
still recommended to set the CLK_QUAL_DIS bit.
Both the ALERT pin and bit (status header) are automatically
cleared if the error is no longer present. The errors related to the
SPI do not recover automatically; read back the appropriate
register to clear the error. The ALERT pin and bit reset in the
next SPI access after the bit is read back.
If a slow clock is not in use and the error triggers, a reset is required.
Reset Detection
If an error detector is manually disabled, it does not generate an
internal error and, consequently, the register map or the
ALERT pin and bit are not triggered.
The AD7771 general error register contains a RESET_DETECTED
bit. This bit is asserted if a reset pulse is applied to the AD7771
and is cleared by reading the general error register. This bit
indicates that the power-on reset (POR) initialized correctly on
the device. In addition, this bit can be used to detect an unexpected
device reset or glitch on the
in SPI control mode, toggle the
general error register, GEN_ERR_REG_2. To reset this error
There are different sources of errors, as described in Table 28. In
pin control code, it is not possible to check the error source, and
some sources of error are not enabled. In SPI control mode, check
the source of an error by reading the appropriate register bit.
RESET
pin. To reset this error signal
SYNC_IN
pin or read from the
The STATUS_REG_x register bits identify the register that
generates an error, as summarized in Table 28.
SYNC_IN
signal in pin control mode, toggle the
pin.
Table 28. Register Error Source
Bit Name
ERR_LOC_GEN2
ERR_LOC_GEN1
ERR_LOC_CH7
ERR_LOC_CH6
ERR_LOC_CH5
ERR_LOC_CH4
ERR_LOC_CH3
ERR_LOC_CH2
ERR_LOC_CH1
ERR_LOC_CH0
ERR_LOC_SAT_CH6_7
ERR_LOC_SAT_CH4_5
ERR_LOC_SAT_CH2_3
ERR_LOC_SAT_CH0_1
Internal LDO Status
Register Source
GEN_ERR_REG_2
GEN_ERR_REG_1
CH7_ERR_REG
CH6_ERR_REG
CH5_ERR_REG
CH4_ERR_REG
CH3_ERR_REG
CH2_ERR_REG
CH1_ERR_REG
CH0_ERR_REG
CH6_7_SAT_ERR
CH4_5_SAT_ERR
CH2_3_SAT_ERR
CH0_1_SAT_ERR
The AD7771 has three internal LDOs to regulate the internal
analog and digital supply rails. The LDOs have internal power
supply monitors. Internal comparators monitor and flag errors
with these supplies after they pass a predetermined limit.
The ALDO1_PSM_ERR, ALDO2_PSM_ERR, and DLDO_PSM_
ERR bits indicate either an LDO malfunction, or, if the LDOs
are bypassed, an incorrect external supply.
The internal analog and digital voltage monitors can be disabled
by appropriately selecting the LDO_PSM_TEST_EN bits.
Use the SAR ADC to verify the error.
Additionally, the levels of the internal monitors can be manually
triggered to check if the detector works correctly by appropriately
setting the LDO_PSM_TRIP_TEST_EN bits. These bits increase
the comparator window threshold above the LDO outputs,
forcing the comparator to trigger.
In addition, the STATUS_REG_x registers have a bit that indicates
if any internal error bit is set, CHIP_ERROR. This bit clears if the
error is no longer present and the register is read back.
ROM and Memory Map CRC
If an error is found at power-up during the ROM verification,
or if the internal memory map is corrupted, the AD7771
generates an error and sets MEMMAP_CRC_ERR or ROM_
CRC_ERR, depending on the source of the error.
The INIT_COMPLETE bit in the STATUS_REG_3 indicates
that the device is initialized correctly. This bit is not an error bit but
an indicator.
General Errors
The checker can be disabled by clearing the MEMMAP_
CRC_TEST_EN and ROM_CRC_TEST_EN bits.
MCLK Switch Error (SPI Control Mode)
After power-up, the AD7771 initiates a clocking handover
sequence to pass clocking control to the external oscillator, or
The device must be reset if any of these errors trigger.
Rev. 0 | Page 49 of 98
AD7771
Data Sheet
Σ-Δ ADC Errors
Output Saturation
Reference Detect (SPI Control Mode)
An output saturation event can occur when gain and offset
calibration causes the output from the digital filter to clip at
either positive or negative full scale. The output does not wrap.
Reading the CHx_ERR_OUTPUT_SAT bit clears the bit if the
error corrects itself.
In SPI control mode, the AD7771 includes on-chip circuitry to
detect if there is a valid reference for conversions or calibrations. If
the voltage between the selected REFx+ and REFx− pins goes
below 0.7 V, the AD7771 detects that it no longer has a valid
reference. CHx_ERR_REF_DET can be interrogated to identify
the affected channel, which clears the bits if the error is no
longer present. The voltage detector can be disabled by clearing
the REF_DET_TEST_EN bit.
The detection can be disabled by clearing OUTPUT_SAT_
TEST_EN bit.
SPI Transmission Errors (SPI Control Mode)
All SPI errors clear after reading GEN_ERR_REG_1, which
contains the SPI errors. These errors are not recovered automatically
and, consequently, the ALERT pin and the ALERT bit remain
set until the error register is read back.
Use the Σ-Δ ADC diagnostic or the SAR ADC to verify the error.
Overvoltage and Undervoltage Events
The AD7771 includes on-chip overvoltage/undervoltage
circuitry on each analog input pin. When the voltage on an
analog input pin goes above AVDD1x + 0.04 mV, the CHx_
ERR_AINx_OV bit is set. The error disappears if the input
voltage falls below AVDD1x − 40 mV.
CRC Checksum Error
If the CRC checksum is enabled by setting the SPI_CRC_
TEST_EN bit, an error bit, SPI_CRC_ERR, is raised if the CRC
message does not match the message computed by the AD7771
internal CRC block. If the CRC message does not match the
internally computed message, the register is not updated.
If an undervoltage event occurs (AVSSx − 40 mV), the CHx_
ERR_AINx_UV bit is set. The error disappears if the input
voltage increases to AVSSx + 0.04 V.
SCLK Counter
The CHx_ERR_AINM_UV, CHx_ERR_AINM_OV, CHx_ERR_
AINP_UV, and CHx_ERR_AINP_OV bits can be read back to
verify the affected channel input, which clears the bits if the
error is no longer present. The overvoltage and undervoltage
detection can be disabled independently by clearing the AINM_
UV_TEST_EN, AINM_OV_TEST_EN, AINP_UV_TEST_EN,
or AINP_OV_TEST_EN bit.
If the number of clocks generated by the controller is not a
CS
multiple of 8 after
is pulled high, an error bit, SPI_CLK_
COUNT_ERR is raised. The last command multiple of 8 is
executed; however, the SCLK counter can be disabled by setting
the SPI_CLK_COUNT_TEST_EN bit.
Invalid Read
When attempting to read back an invalid register address, the
SPI_INVALID_READ_ERR bit is set.
The input voltage can be checked independently with the
SAR ADC.
The invalid readback address detection can be disabled by
setting the SPI_INVALID_READ_TEST_EN bit.
Modulator Saturation
The AD7771 includes modulator saturation detection on each
of the Σ-Δ ADCs. If 20 consecutive codes for the modulator
are either all 1s or 0s, this condition is flagged as a modulator
saturation event. Reading CHx_ERR_MOD_SAT clears the bit
if the error corrects itself.
Invalid Write
When attempting to write to an invalid register address, the
SPI_INVALID_WRITE_ERR bit is set.
The invalid write address detection can be disabled by setting
the SPI_INVALID_WRITE_TEST_EN bit.
Modulator saturation detection can be disabled by clearing the
MOD_SAT_TEST_EN bit.
MONITORING USING THE AD7771 SAR ADC
(SPI CONTROL MODE)
Note that the modulator input voltage is attenuated internally,
which means that a modulator output of all 1s or 0s represents a
The AD7771 contains an on-chip SAR ADC for chip diagnostics,
system diagnostics, or measurement verification. The SAR ADC
has a 12-bit resolution. The AVDD4 and AVSS4 pins operate in
complete independence of the Σ-Δ ADC supplies and, therefore,
can be used for chip diagnostics in systems where functional
safety is important. The reference for the SAR conversion
process is taken from the SAR ADC supply voltage (AVDD4/
AVSS4) and, therefore, the SAR analog input range is from AVSS4
to AVDD4.
RESET
modulator that is out of bounds and that a
pulse is required.
Filter Saturation
TheAD7771 includes digital filter saturation detection on each
Σ-Δ ADC channel. This detection indicates that the filter output is
out of bounds, which represents an output code approximately 20%
higher than positive or negative full scale. Reading the CHx_ERR_
FILTER_SAT bit clears the bit if the error corrects itself.
The detection can be disabled by clearing FILTER_SAT_TEST_
EN bit.
Rev. 0 | Page 50 of 98
Data Sheet
AD7771
The SAR ADC has a maximum throughput rate of 256 kSPS.
The CONVST_SAR pin initiates a conversion on the SAR ADC.
The maximum allowable frequency of the CONVST_SAR pin is
256 kHz. If consecutive conversions are performed in the SAR
ADC, read back the result from the previous conversion before
a new conversion is generated. Otherwise, the results are
corrupted.
Use the auxiliary inputs, AUXAIN+ and AUXAIN−, to validate
the Σ-Δ measurements. While operating in SPI control mode,
the AD7771 has three available GPIOx ports controlled via the
SPI. The GPIOx pins can be used to control an external, dual
8:1 multiplexer, which, in turn, samples the eight Σ-Δ channels.
Use this diagnostic in applications where functional safety is
required. This diagnostic aids in removing the need for a
secondary external ADC to validate primary measurements on
the Σ-Δ channels.
The SAR ADC is only available in SPI control mode. To read
conversion results from the SAR ADC, set the SAR_DIAG_
MODE_EN bit. After this bit is set, all data shifted out from the
SDO pin originates from the SAR ADC conversion, as shown in
Figure 121.
Temperature Sensor
The internal die temperature can be measured with an accuracy
of 2°C. The differential voltage base emitter (DVBE) is
proportional to the temperature measured referred to 25°C.
The CONVST_SAR signal can be internally deglitched to avoid
false triggers.
DVBE − 0.6 V
Temperature (°C) =
2 mV
Table 29. SAR Synchronization and Deglitching
CONVST_DEGLITCH_DIS
(Register 0x013, Bits[7:6]) Effect on CONVST_SAR
Table 30. SAR Mux Inputs
SAR
Input
Positive
Signal
Negative
Signal
11
10
CONVST_SAR goes directly to the SAR
CONVST_SAR reaches the SAR when
it is 1.5/MCLK cycles wide
Attenuation ÷ 6
0
1
2
3
4
5
6
7
AUXAIN+
DVBE
REF1+
REF2+
REF_OUT
VCM
AREG1CAP
AREG2CAP
DREGCAP
AVDD1A
AVDD1B
AVDD2A
AVDD2B
IOVDD
AVDD4
DGND
AUXAIN−
AVSSx
REF1−
REF2−
AVSSx
AVSSx
AVSSx
AVSSx
DGND
AVSSx
AVSSx
AVSSx
AVSSx
DGND
AVSSx
AVSSx
AVSSx
AVSSx
AVSSx
AVSSx
AVSSx
AVDD4
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
Yes
Yes
No
No
Yes
Increase the acquisition time by 1.5/MCLK when the deglitch
circuitry is enabled.
Prior to the SAR ADC, the AD7771 contains an internal
multiplexer. This multiplexer can be configured over the SPI to
set the inputs to the SAR ADC to be either internal circuit
nodes (in the case of diagnostics) or to select the external
AUXAIN+ and AUXAIN− pins.
8
9
Along with converting external voltages, the SAR ADC monitors
the internal nodes on the AVDD, IOVDD, and DGND pins, and
the DLDO and analog LDO (ALDO) outputs. Some voltages are
internally attenuated by 6, and the resulting voltage is applied to
the SAR ADC, as shown in Table 30. This is useful because
variations in the power supply voltage can be monitored.
10
11
12
13
14
15
16
17
18
19
20
21
The input multiplexer of the SAR is controlled by the GLOBAL_
MUX_CONFIG register, and the different inputs available are
described in Table 30.
DGND
DGND
AVDD4
REF1+
REF2+
The SAR ADC also contains an SAR driver amplifier, as shown
in Figure 122. This amplifier settles the SAR input to 12-bit
accuracy within the t33 time. This driver amplifier helps
minimize the kickback from the SAR converter to the global
diagnostic mux input circuit nodes.
AVSSx
CS
SET BIT 5
GENERAL_USER_CONFIG_2 REG
WRITE TO ADC MUX REGISTER
ADC CONVERSION RESULT REG
WRITE TO ADC MUX REGISTER
ADC CONVERSION RESULT REG
SDI
SDO
Figure 121. Configuring the AD7771 to Operate the SPI to Read from the SAR ADC
Rev. 0 | Page 51 of 98
AD7771
Data Sheet
AVDD4
AVSS4
DEGLITCH
CONVST_SAR
AUXAIN+
AUXAIN–
REF
FIFO
SAR ADC
MUX
SAR DRIVER
CONTROL LOGIC
SPI
ON-CHIP
DIAGNOSTICS
Figure 122. SAR ADC Configuration and Control
Table 31. Σ-Δ Diagnostic
Input
Voltage
Floating
Floating
Recommended Voltage Reference
Not applicable
Not applicable
Internal/external
External
External
External
Internal
Internal
Notes/Result
0
1
2
3
4
5
6
7
8
9
Not applicable
Not applicable
PGA gain verification
Positive full scale
Negative full scale
Zero scale
Positive full scale
Negative full scale
Zero scale
280 mV differential signal
External reference, positive/negative
External reference, negative/positive
External reference, negative/negative
Internal reference, positive/negative
Internal reference, negative/positive
Internal reference, positive/positive
External reference, positive/positive
Internal
External
Zero scale
There are two different ways to enable the diagnostic mux, as
follows:
Σ-Δ ADC DIAGNOSTICS (SPI CONTROL MODE)
The AD7771 Σ-Δ ADC diagnostic functions are accessible
through the SPI. The internal mux placed before the PGA has
different inputs, allowing the user to select a zero-scale, positive
full-scale, or negative full-scale input to the Σ-Δ ADC, which
can be converted to verify the correct operation of the
Σ-Δ ADC channel.
•
Setting the CHx_RX bit. This bit enables the input Σ-Δ
mux. The multiplexer inputs are described in Table 31. The
reference used during the conversions are controlled by the
REF_MUX_CTRL bits.
•
Setting CHx_REF_MONITOR. This bit has the same effect
as enabling the CHx_RX bit and selects the VDD1x/
AVSSx supplies as the main reference.
The diagnostic mux control signals are shared across all the Σ-Δ
channels. Depending on the diagnostic selected, connect the
Σ-Δ ADC reference to a different reference source to guarantee
that the conversion is within the measurable range.
If the AINx pin is connected to AVSSx, the input range is
outside the range of AVSSx + 100 mV; therefore, results may
differ slightly from the expected value.
Alternatively, the inputs can be used to calibrate gain and offset
errors.
Rev. 0 | Page 52 of 98
Data Sheet
AD7771
Σ-∆ OUTPUT DATA
ADC CONVERSION OUTPUT—HEADER AND DATA
Table 32. Channel ID
Channel
CH_ID_2
CH_ID_1
CH_ID_0
The AD7771 Σ-Δ conversion results are output on the DOUT0
to DOUT3 pins or over the SPI, depending on the selected
interface. If the DOUTx interface is selected, the AD7771 acts
as the master in the transmission. If the SPI is selected, the
controller is the master.
0
1
2
3
4
5
6
7
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
DRDY
The
signal indicates the end of conversion independent of
the interface selected to read back the Σ-Δ conversion. When
the SPI reads back the Σ-Δ conversion, if a new conversion is
DRDY
completed (
falling edge) before the previous conversion is
read back, the results from previous conversion are overwritten
and, consequently, the previous conversion data is corrupted.
The CRC generated is eight bits long; the 4 MSBs are placed on the
header for the first channel in the pairing and the 4 LSBs on the
header of the second channel in the pairing, as shown in
Table 33. If a channel is disabled, the 24-bit output data for this
channel is 0x000000.
For each channel, the width is 32 bits long: 8 bits for the header
and 24 bits for the Σ-Δ conversion, as shown in Figure 123.
DRDY
Table 33. 8-Bit CRC, Header Configuration (Channel 2)
CE
0
1
0
CRC7
CRC6
CRC5
CRC4
ADC DATA N
24-BITS
DOUTx N – 1
HEADER N
8-BITS
Table 34. 8-Bit CRC, Header Configuration (Channel 3)
CE CRC3 CRC2 CRC1 CRC0
0
1
1
Figure 123. ADC Output—8-Bit Header Plus 24-Bit Conversion Data
In pin control mode, the header is fixed to the CRC while in SPI
mode, and can be selected between the CRC and error headers.
Error Header (SPI Control Mode)
In SPI control mode, the default header can be replaced by an
error header. If the Σ-Δ conversion is read back through the
SPI, disable the CRC by clearing the SPI_CRC_TEST_EN bit. If
the DOUTx interface is used, clear the DOUT_HEADER_
FORMAT bit.
CRC Header
The CRC header is the header generated in pin control mode or
in SPI control mode if DOUT_HEADER_FORMAT is set.
As shown in Figure 124, the header consists of an alert bit,
three bits for the ADC channel ID, as shown in Table 32, and
four bits for the CRC.
The error header provides information of common error
sources specific for each channel, as shown in Table 35.
Modulator and filter errors are indicated even if the checker for
these errors are specifically disabled, as described in the Σ-Δ
ADC Errors section.
The alert bit is set high if an error is detected in any channel, as
explained in the General Errors section. The alert bit remains
set to 1 until the error disappears.
CHANNEL CHANNEL CHANNEL
ALERT
CRC CRC CRC CRC
NUMBER
NUMBER
NUMBER
Figure 124. CRC Header
Table 35. Status Header Output
Bits Name
Description
7
Alert
This bit is set high if any of the enabled diagnostic functions have detected an error, including an
external clock not detected, a memory map bit flip, or an internal CRC error. This bit is not channel specific.
This bit clears if the error is no longer present.
6:4
3
2
CH_ID_[2:0]
RESET_DETECTED
MODULATOR_SATURATE
These bits indicate which ADC channel the following conversion data came from (see Table 32).
This bit indicates if a reset condition occurs. This bit is not channel specific.
This bit indicates that the modulator output is 20 consecutive 0s or 1s. The bit resets automatically
after the error is no longer present.
1
0
FILTER_SATURATE
AIN_OV_UVERROR
This bit indicates that the filter output is out of bounds. The bit resets automatically after the error is
no longer present.
This bit indicates that there is an AINx overvoltage/undervoltage condition on the inputs. This bit is
set until the appropriate register is read back and the error is no longer present.
Rev. 0 | Page 53 of 98
AD7771
Data Sheet
The ODR can be updated on the fly, but a new ODR is effective
in three conversion cycles of the Σ-Δ ADCs. This condition
guarantees a smooth transition with no conversion results out
of range.
SAMPLE RATE CONVERTER (SRC) (SPI CONTROL
MODE)
The AD7771 implements a patented featured called the SRC on
each Σ-Δ channel that allows the user to configure the output
data rate or sampling frequency to any desired value, including
noninteger values. The SRC achieves fine resolution control
over the Σ-Δ ADC ODR, up to 15.2 µSPS. In applications where
the ODR must change based on changes in the input signal to
maintain sampling coherency, the SRC provides fine control
over the ODR. For example, to achieve the highest classification
standard, Class A, in power quality applications, coherency
must be maintained for 0.01 Hz changes in the input power
line. Use the SRC to achieve this sampling frequency accuracy.
There are two different ways to change the ODR after a new
value is written in the SRC registers: via software or via
hardware, depending on the SRC_LOAD_SOURCE bit
(SRC_UPDATE register, Bit 7).
If the SRC_LOAD_SOURCE bit is clear, the new ODR value is
updated by setting the SRC_LOAD_UPDATE bit to 1. This bit
must be held high for at least two MLCK periods; return the bit
to 0 before attempting another update.
If SRC_LOAD_SOURCE is set, the GPIO0 pin controls the ODR
update externally. Apply a pulse in the GPIO2 pin, which is then
internally synchronized with the external MCLK clock, and the
resultant synchronous signal is output on the GPIO1 pin.
In pin control mode, the ODR is fixed per the predefined pin
control options. Consequently, a noninteger number cannot be
selected, as shown in Table 13.
To set the ODR, the user must program up to four registers,
depending on the decimation value: two registers to program the
integer value, N (the effective decimation rate), and two registers
to program the decimal value, the interpolation factor (IF).
The GPIO1 and GPIO0 pins must be externally connected.
If multiple AD7771 devices must be synchronized, the GPIO1 pin
of one device can be connected to multiple devices. This synchro-
nization method requires the use of a common MCLK signal for all
the AD7771 devices connected, as shown in Figure 125.
The integer value registers are SRC_N_MSB, Bits[3:0] and
SRC_N_LSB, Bits[7:0]. The decimal part value registers are
SRC_IF_MSB, Bits[7:0] and SRC_IF_LSB, Bits[7:0].
PULSE
AD7771
As an example, if an output data rate of 2.8 kHz is required, the
decimation rate equates to
GPIO2
GPIO1
MCLK
SYNCHRONIZATION
LOGIC
•
•
High resolution mode = 2048/2.8 = 731.428
Low power mode = 512/2.8 = 182.857
DIGITAL FILTER
GPIO0
The register values for high resolution mode are as follows:
•
•
•
•
•
•
731 (decimal) = 0x2DB
SRC_N_MSB, Bits[3:0] = 0x02
SRC_N_LSB, Bits[7:0] = 0xDB
AD7771
0.428 (decimal) = 0.428 × 216 = 28049 (decimal) = 0x6D91
SRC_IF_MSB, Bits[7:0] = 0x6D
SRC_IF_LSB, Bits[7:0] = 0x91
GPIO2
GPIO1
MCLK
SYNCHRONIZATION
MCLK
NC
LOGIC
DIGITAL FILTER
The SRC resolution depends on the decimal number used in the
decimation, as well as the modulator clock (MOD_MCLK), as
follows:
GPIO0
MODMCLK
16 ×DEC2 + 3×DEC + 2×
AD7771
Resolution =
GPIO2
1
2
MCLK
GPIO1
SYNCHRONIZATION
216
NC
LOGIC
where:
MODMCLK is the modulator frequency.
DIGITAL FILTER
GPIO0
DEC is the decimal portion of the decimation rate.
In high resolution mode, for a decimal decimation of 450, the
resolution is defined as
Figure 125. Hardware ODR Update
2048
= 15.2 ×10–6 SPS
1
2
16 × 4502 + 3× 4502 ×
216
Rev. 0 | Page 54 of 98
Data Sheet
AD7771
40
35
30
25
20
15
10
5
SRC Bandwidth
The sinc3 and sinc5 filters architecture allows the user to select
a noninteger value as the decimation range This versatility
means that the filter notches must be adjusted dynamically:
two notches (sinc3) or four notches (sinc5) at the variable
frequency, and one fixed notch to remove the PGA chopping
tone. Consequently, the traditional formula for the −0.1 dB and
−3 dB bandwidth must be adjusted depending on the selected
decimation rate.
y = 0.2653x + 634.03
The bandwidth transfer function is not linear but can be
approximated by using a linear function.
0
Figure 126 to Figure 129 show the correction factor for the
−0.1 dB and −3 dB bandwidth, respectively. In low power mode,
the offset must be divided by 4. For example, for sinc5 when the
ODR = 1000 SPS, the −0.1 dB point is
0
50
100
ODR (kHz)
Figure 128. −3 dB Correction Factor, Sinc3 Filter Enabled
30
25
20
15
10
5
49.355
BW = 0.0377 × 1000 +
= 50.03 Hz
4
7
6
y = 0.2053x + 263.94
5
y = 0.049x + 120.41
4
3
2
1
0
0
50
100
ODR (kHz)
Figure 129. −3 dB Correction Factor, Sinc5 Filter Enabled
0
0
SRC Group Delay
50
100
ODR (kHz)
The SRC group delay depends on the selected ODR and is
defined by the following equation:
Figure 126. −0.1 dB Correction Factor, Sinc3 Filter Enabled
6
PM + SRC _ N
SRC Group Delay =
SRC _ N ×ODR
5
where:
4
PM is a constant equal to 8.
y = 0.0377x + 49.355
SRC_N is the integer value of the programmed ODR.
ODR is the programmed output data rate.
3
When using the sinc5 filter, the equation that defines the group
delay is
2
1
0
PM + 2×SRC _ N
SRC Group Delay =
SRC _ N ×ODR
0
50
100
The latency is the contribution of the group delay and the
calibration time.
ODR (kHz)
Figure 127. −0.1 dB Correction Factor, Sinc5 Filter Enabled
Latency = Group Delay + tCAL
In high resolution mode, the calibration delay is defined as 62 ×
tMCLK, with a maximum error of 2 × tMCLK. In low power mode,
the calibration delay is defined as 121 × tMCLK, with a maximum
error of 4 × tMCLK. tMCLK is the modulator period and is 488 ns in
high resolution mode and 1.9 µs in low power mode.
Rev. 0 | Page 55 of 98
AD7771
Data Sheet
Settling Time
is configured in SPI control mode, the SPI_SLAVE_MODE_
EN bit enables the SPI to transmit the Σ-Δ ADC conversion
results, as shown in Table 22.
The settling time is defined by the contribution of all the internal
stages, the filter delay, and the block calibration.
DOUT3 to DOUT0 Data Interface
When using the sinc3 filter option, the filter delay is defined as
3/ODR. In some extreme cases, such as when an external pulse is
applied, this value may increase to 4/ODR. If using the sinc5 filter,
the filter delay is defined as 5/ODR, or 6/ODR for extreme cases.
Standalone Mode
In standalone mode, the AD7771 interface acts as a master.
There are three different DOUT configurations, configurable
through the FORMATx pins in pin control mode, as shown in
Figure 130 through Figure 132, or via the DOUT_FORMAT bits,
Bits[7:6], in SPI control mode, as described in Table 36.
DATA OUTPUT INTERFACE
The Σ-Δ output data interface is defined by the CONVST_SAR,
FORMAT0, and FORMAT1 pins in pin control mode at power-up.
The FORMATx pins cannot be changed dynamically. Table 14
shows the available options for pin control mode. If the device
Figure 133, Figure 134, and Figure 135 show the expected data
outputs for different DOUTx output modes.
Table 36. DOUTx Channels
DOUT_FORMAT Bits/
FORMATx Pins
Number of DOUTx
Lines Enabled
Associated Channels
00
4
DOUT0—Channel 0 and Channel 1
DOUT1—Channel 2 and Channel 3
DOUT2—Channel 4 and Channel 5
DOUT3—Channel 6 and Channel 7
01
2
1
DOUT0—Channel 0, Channel 1, Channel 2, and Channel 3
DOUT1—Channel 4, Channel 5, Channel 6, and Channel 7
10 or 11
DOUT0—Channel 0, Channel 1, Channel 2, Channel 3, Channel 4, Channel 5,
Channel 6, and Channel 7
AD7771
DRDY
DCLK
CH 0
CH 0
CH 0
CH 0
CH 1
CH 1
CH 1
CH 1
DOUT0
DOUT1
DOUT2
DOUT3
00
FORMAT0
FORMAT1
DOUT0: CH 0, CH 1
DOUT1: CH 2, CH 3
DOUT2: CH 4, CH 5
DOUT3: CH 6, CH 7
0
0
DGND
DAISY-CHAINING IS
NOT POSSIBLE IN THIS FORMAT
Figure 130. FORMATx Pin Configuration—FORMAT0 = 0, FORMAT1 = 0
AD7771
DRDY
DCLK
IOVDD
01
CH 0 CH 1 CH 2 CH 3
CH 4 CH 5 CH 6 CH 7
DOUT0
DOUT1
CH 0, CH 1, CH 2, CH 3
OUTPUT ON DOUT0
FORMAT0
FORMAT1
1
0
CH 4, CH 5, CH 6, CH 7
OUTPUT ON DOUT1
DGND
DAISY-CHAINING IS
POSSIBLE IN THIS FORMAT
Figure 131. FORMATx Pin Configuration—FORMAT0 = 1, FORMAT1 = 0
AD7771
DRDY
DCLK
DGND
10
FORMAT0
FORMAT1
CH 0 TO CH 7
OUTPUT ON DOUT0
0
1
DOUT0
CH 0 CH 1 CH 2 CH 3 CH 4 CH 5 CH 6 CH 7
IOVDD
DAISY-CHAINING IS
POSSIBLE IN THIS FORMAT
Figure 132. FORMATx Pin Configuration—FORMAT0 = 0, FORMAT1 = 1
Rev. 0 | Page 56 of 98
Data Sheet
AD7771
DCLK
SAMPLE N
SAMPLE N + 1
DRDY
DOUT0
CH0-S0
CH2-S0
CH4-S0
CH6-S0
CH1-S0
CH3-S0
CH5-S0
CH7-S0
CH0-S1
CH2-S1
CH4-S1
CH6-S1
CH1-S1
CH3-S1
CH5-S1
CH7-S1
DOUT1
DOUT0
DOUT1
Figure 133. FORMAT0 = 0, FORMAT1 = 0—Each DOUTx Outputs Two ADC Conversions (S0 Means Sample 0 and S1 Means Sample 1)
DCLK
SAMPLE N
SAMPLE N + 1
DRDY
DOUT0
DOUT1
DOUT2
CH0-S0
CH4-S0
CH1-S0
CH5-S0
CH2-S0
CH3-S0
CH7-S0
CH0-S1
CH4-S1
CH1-S1
CH2-S1
CH6-S1
CH3-S1
CH7-S1
CH6-S0
CH5-S1
DOUT3
Figure 134. FORMAT0 = 0, FORMAT1 = 1—Channel 0 to Channel 3 Share DOUT0, and Channel 4 to Channel 7 Share DOUT1 (S0 Means Sample 0 and S1 Means Sample 1)
DCLK
SAMPLE N
SAMPLE N + 1
SAMPLE N + 2
DRDY
DOUT0
CH0-S0 CH1-S0 CH2-S0 CH...-S0 CH6-S0 CH7-S0 CH0-S1 CH1-S1 CH2-S1 CH...-S1 CH6-S1 CH7-S2 CH0-S2 CH1-S2 CH2-S2 CH...-S2 CH6-S2 CH7-S2 CH0-S3
DOUT1
DOUT2
DOUT3
Figure 135. FORMAT0 = 1, FORMAT1 = 0—Channel 0 to Channel 7 Output on DOUT0 Only (S0 Means Sample 0 and S1 Means Sample 1)
Rev. 0 | Page 57 of 98
AD7771
Data Sheet
the Digital Reset and Synchronization Pins section for more
information.
Daisy-Chain Mode
Daisy-chaining devices allows numerous devices to use the
same data interface lines by cascading the outputs of multiple
ADCs from separate AD7771 devices. In daisy-chain configura-
tion, only one device has a direct connection between the
DOUTx interface and the digital host. For the AD7771, daisy-
chain capability is implemented by cascading DOUT0 and DOUT1
through a number of devices, or by just using DOUT0 (the
number of DOUTx pins available depends on the selected
DOUTx mode). The ability to daisy-chain devices and the limit
on the number of devices that can be handled by the chain is
dependent on the selected DOUTx mode and the decimation
rate employed.
This feature is especially useful for reducing the component
count and wiring connections in, for example, isolated
multiconverter applications or for systems with a limited
interfacing capacity.
For daisy-chain operation, there are two different configurations
possible, as described in Table 37.
Using the FORMATx = 10 mode, DOUT2 acts as an input pin, as
shown in Figure 136. In this case, the DOUT0 pin of the AD7771
devices is cascaded to the DOUT2 pin of the next device in the
chain. Data readback is analogous to clocking a shift register
where data is clocked on the rising edge of DCLK.
When operating in daisy-chain mode, it is required that all
AD7771 devices in the chain are correctly synchronized. See
Table 37. DOUTx Modes in Daisy-Chain Operation
DOUT_FORMAT Bits/
FORMATx Pins
Number of DOUTx Lines Enabled
Associated Channels
01
2
DOUT0—Channel 0 to Channel 3 and DOUT2
DOUT1—Channel 4 to Channel 7 and DOUT3
DOUT2—input channel
DOUT3—input channel
10
1
DOUT0—Channel 0 to Channel 7 and DOUT2
DOUT2—input channel
U2
U2
DOUT0
DOUT0
DOUT2/DIN0
DOUT2/DIN0
DCLK
DRDY
U2 DOUT2/DIN0
U2 DOUT0
0
0
0
0
0
0
0
U2 S0 CH0 TO CH7
U2 S1 CH0 TO CH7
U2 S0 CH0 TO CH7
U1 DOUT2/DIN0
U1 DOUT0
U2 S0 CH0 TO CH7 U2 S0 CH0 TO CH7 U2 S1 CH0 TO CH7 U2 S1 CH0 TO CH7 U2 S0 CH0 TO CH7
U1 S0 CH0 TO CH7 U1 S0 CH0 TO CH7 U1 S1 CH0 TO CH7 U2 S3 CH0 TO CH7 U1 S1 CH0 TO CH7
Figure 136. Daisy-Chain Connection Mode, FORMAT0 = 1, FORMAT1 = 0 (S0 Means Sample 0 and S1 Means Sample 1); When Connected in Daisy-Chain Mode,
DOUT2 Acts as an Input Pin, Represented by DIN0
Rev. 0 | Page 58 of 98
Data Sheet
AD7771
Table 39. Maximum ODRs and Minimum DCLKx
Frequencies in High Resolution Mode
Minimum DCLKx Frequency
Select the DCLKx frequency ratio in such a way that the data is
completely shifted out before a new conversion is completed;
otherwise, the previous conversion is overwritten and the trans-
mission becomes corrupt. The minimum DCLKx frequency ratio
is defined by the decimation rate, the operation mode, and the
lines enabled on the DOUT3 to DOUT0 data interface as
described in the following equations:
Minimum DCLKx (kHz)1
Decimation ODR
Rate
4095
2048
1024
512
256
128
64
(kSPS)
1 × DOUTx 2 × DOUTx 4 × DOUTx
0.500122 128
1
2
4
64
32
64
256
128
512
256
128
256
512
1024
2048
4096
8192
1024
2048
4096
8192
N/A
512
8
1024
2048
4096
8192
N/A
In standalone, high resolution mode,
16
32
64
128
DCLKMIN_RATIO < Decimation/(8 × DOUT_FORMAT)
In standalone, low power mode,
32
16
N/A
DCLKMIN_RATIO < Decimation/(4 × DOUT_FORMAT)
In daisy-chain, high resolution mode,
1 N/A means not applicable.
Table 40. Maximum ODRs and Minimum DCLK
Frequencies in Low Power Mode
DCLKMIN_RATIO < Decimation/(8 × Devices × DOUTx Channels)
In daisy-chain, low power mode,
Minimum DCLKx (kHz)
Decimation ODR
DCLKMIN_RATIO < Decimation/(4 × Devices × DOUTx Channels)
Rate
2048
1024
512
256
128
64
(kSPS) 1 × DOUTx 2 × DOUTx 4 × DOUTx
As an example, when operating in master interface mode,
FORMATx = 01, the DOUT0 and DOUT1 pins shift out four
Σ-Δ channels each and, assuming a maximum output rate in
high resolution mode, the decimation = 128.
0.25
0.5
1
64
128
256
32
64
16
32
64
128
256
512
1024
2048
128
256
512
1024
2048
4096
2
512
4
8
16
32
1024
2048
4096
N/A1
DCLKMIN < 128/(8 × 4) = 4
If the DCLKMIN_RATIO is selected above the necessary minimum,
a Logic 0 is continuously transmitted until a new sample is
available.
32
16
1 N/A means not applicable.
An example in daisy-chain mode, assuming FORMATx = 01,
and with three devices connected and a decimation rate of 256
in high resolution mode, is as follows:
If the AD7771 operates in SPI control mode, it is possible to
adjust the DOUTx strength, which can be selected in the
DOUT_DRIVE_STR bits, as described in Table 41.
DCLKMIN_RATIO < 256/(8 × 3 × 4) = 2.66 = 2
Table 41. DOUTx Strength
The different ratios are summarized in Table 38.
DOUT_DRIVE_STR
Mode
Table 38. Available DCLK Ratios
DCLK_CLK_DIV (SPI Control Mode),
DCLKx (Pin Control Mode)
00
01
10
11
Nominal
Strong
Weak
DCLKx Ratio
000
001
010
011
100
101
110
111
1
2
4
8
16
32
64
128
Extra strong
SPI
The SPI gives the user flexibility to read the conversion from the
Σ-Δ ADC where the processor or microcontroller is the master.
DRDY
When a new conversion is completed, the
toggled to indicate that data can be accessed. When
signal is
DRDY
toggles, the internal channel counter is reset and the next SPI
read originates from Channel 0 again. Conversely, after the last
There are maximum achievable ODRs and minimum DCLKx
frequencies required for a given DOUTx pin configuration, as
shown in Table 39 and Table 40.
DRDY
channel data is read, all successive reads before the next
signal originate from Channel 7 (LSB).
Rev. 0 | Page 59 of 98
AD7771
Data Sheet
CS
CH0_HEADER _+_CH0_8_BITS_MSB
CH0_16_BITS_LSB
SDO
Figure 137. SPI Readback, 16 Bits per Frame
CS
CH0_HEADER _+_CH0_16_BITS_MSB
CH0_8_BITS_LSB_+_CH1_HEADER_+CH1_8_BITS_MSB
SDO
Figure 138. SPI Readback, 24 Bits per Frame
The SPI operates in multiples of 8 bits per frame; Figure 137 shows
a readback example in 16 bits per frames, and Figure 138 shows a
readback in 24 bits per frame.
Σ-Δ CRC Checksum
The CRC message is calculated internally by the AD7771 on
ADC pairs. The CRC is calculated using the ADC output data
from two ADCs and Bits[7:4] from the header. Therefore, 56 bits
are used to calculate the 8-bit CRC. This CRC is split between
the two channel headers. The CRC data covers channel pairings
as follows: Channel 0 and Channel 1, Channel 2 and Channel 3,
Channel 4 and Channel 5, and Channel 6 and Channel 7.
Note that if the device is configured in SPI control mode, the
AD7771 generates a software reset if the SDI pin is sampled
high for 64 consecutive clocks. To avoid a reset or unwanted
register writes, it is recommended to transfer a 0x8000 command,
which generates a readback command that is ignored by the
device, as explained in the SPI Software Reset section.
To generate the checksum, the data is left shifted by eight bits to
create a number ending in eight Logic 1s.
CALCULATING THE CRC CHECKSUM
The AD7771 implements two different CRC checksum
generators, one for the Σ-Δ results and another for the SPI
control mode.
The CRC is calculated from 56 bits across two consecutive/
channel pairings (Channel 0 and Channel 1, Channel 2 and
Channel 3, Channel 4 and Channel 5, Channel 6, and Channel 7).
The 56 bits consist of the alert bit, the 3 bits for the first ADC
pairing channel, and the 24 bits of data of each pairing channel.
For example, for the second channel pairing, Channel 2 and
Channel 3,
The AD7771 uses a CRC polynomial to calculate the CRC
checksum value. The 8-bit CRC polynomial used is x8 + x2 + x + 1.
The polynomial is aligned so that its MSB is adjacent to the
leftmost Logic 1 of the data. An exclusive OR (XOR) function is
applied to the data to produce a new, shorter number. The
polynomial is again aligned so that its MSB is adjacent to the
leftmost Logic 1 of the new result, and the procedure is
repeated. This process is repeated until the original data is
reduced to a value less than the polynomial. This is the 8-bit
checksum.
56 bits = alert bit + 3 ADC channel bits (010) + 24 data bits
(Channel 2) + alert bit + 3 ADC channel bits (011) +
24 data bits (Channel 3)
SPI Control Mode Checksum
The CRC message is calculated internally by the AD7771. The
data transferred to the AD7771 uses the R/W bit, a 7-bit address,
and 8 bits of data for the CRC calculation.
An example of CRC calculation for 12-bit data is shown in
Table 42.
The CRC calculated and appended to the data that is shifted
out uses a 0010 0000 header and 8 bits of data for the register
readback, as well as the 0010 header and 12 bits of SAR conversion
data for the SAR readback transfers.
Table 42. Example CRC Calculation for 12-Bit Data1
Data
0
1
1
0
1
1
0
0
0
0
0
0
0
0
0
1
0
1
0
1
0
0
0
0
0
0
1
1
0
1
1
1
0
1
1
1
1
1
1
0
0
0
Polynomial
1
1
1
1
CRC
1 This table represents the division of the data; blank cells are for formatting
purposes.
Rev. 0 | Page 60 of 98
Data Sheet
AD7771
REGISTER SUMMARY
Table 43. Register Summary
Reg.
Name
Bits
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset
R/W
0x000 CH0_CONFIG
0x001 CH1_CONFIG
0x002 CH2_CONFIG
0x003 CH3_CONFIG
0x004 CH4_CONFIG
0x005 CH5_CONFIG
0x006 CH6_CONFIG
0x007 CH7_CONFIG
0x008 CH_DISABLE
[7:0]
CH0_GAIN
CH0_REF_
MONITOR
CH0_RX
RESERVED
0x00
/W R
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
CH1_GAIN
CH2_GAIN
CH3_GAIN
CH4_GAIN
CH5_GAIN
CH6_GAIN
CH7_GAIN
CH6_
CH1_REF_
MONITOR
CH1_RX
CH2_RX
CH3_RX
CH4_RX
CH5_RX
CH6_RX
CH7_RX
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
CH1_
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x24
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
CH2_REF_
MONITOR
CH3_REF_
MONITOR
CH4_REF_
MONITOR
CH5_REF_
MONITOR
CH6_REF_
MONITOR
CH7_REF_
MONITOR
CH7_
CH5_DISABLE
CH4_
DISABLE
CH3_
DISABLE
CH2_
DISABLE
CH0_
DISABLE
DISABLE
DISABLE
DISABLE
0x009 CH0_SYNC_
OFFSET
CH0_SYNC_OFFSET
CH1_SYNC_OFFSET
CH2_SYNC_OFFSET
CH3_SYNC_OFFSET
CH4_SYNC_OFFSET
CH5_SYNC_OFFSET
CH6_SYNC_OFFSET
CH7_SYNC_OFFSET
0x00A CH1_SYNC_
OFFSET
0x00B CH2_SYNC_
OFFSET
0x00C CH3_SYNC_
OFFSET
0x00D CH4_SYNC_
OFFSET
0x00E CH5_SYNC_
OFFSET
0x00F CH6_SYNC_
OFFSET
0x010 CH7_SYNC_
OFFSET
0x011 GENERAL_
USER_
ALL_
POWER-
MODE
PDB_VCM
PDB_
REFOUT_BUF SAR
PDB_
PDB_
RC_OSC
SOFT_RESET
CH_DIS_
MCLK_EN
CONFIG_1
0x012 GENERAL_
USER_
[7:0]
[7:0]
[7:0]
RESERVED FILTER_
MODE
SAR_DIAG_
MODE_EN
SDO_DRIVE_STR
DOUT_DRIVE_STR
SPI_SYNC
0x09
0x80
0x20
R/W
R/W
R/W
CONFIG_2
0x013 GENERAL_
USER_
CONVST_
DEGLITCH_DIS
RESERVED
SPI_SLAVE_
MODE_EN
RESERVED
CLK_
QUAL_DIS
CONFIG_3
0x014 DOUT_FORMAT
DOUT_FORMAT
REF_MUX_CTRL
DOUT_
HEADER_
FORMAT
RESERVED
DCLK_CLK_DIV
RESERVED
0x015 ADC_MUX_
CONFIG
[7:0]
[7:0]
MTR_MUX_CTRL
RESERVED
RESERVED
GPIO_OP_EN
0x00
0x00
R/W
R/W
0x016 GLOBAL_MUX_
CONFIG
GLOBAL_MUX_CTRL
RESERVED
0x017 GPIO_CONFIG
0x018 GPIO_DATA
[7:0]
[7:0]
[7:0]
0x00
0x00
0x38
R/W
R/W
R/W
RESERVED
GPIO_READ_DATA
GPIO_WRITE_DATA
RESERVED
0x019 BUFFER_
CONFIG_1
RESERVED
REF_BUF_
POS_EN
REF_
BUF_
NEG_EN
0x01A BUFFER_
CONFIG_2
[7:0]
REF-
BUFP_
PREQ
REF-
BUFN_
PREQ
RESERVED
PDB_
PDB_
PDB_
DLDO_
OVRDRV
0xC0
R/W
ALDO1_OVR ALDO2_
DRV OVRDRV
0x01C CH0_OFFSET_
UPPER_BYTE
[7:0]
[7:0]
CH0_OFFSET_ALL[23:16]
CH0_OFFSET_ALL[15:8]
0x00
0x00
R/W
R/W
0x01D CH0_OFFSET_
MID_BYTE
Rev. 0 | Page 61 of 98
AD7771
Data Sheet
Reg.
Name
Bits
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset
R/W
0x01E CH0_OFFSET_
LOWER_BYTE
[7:0]
CH0_OFFSET_ALL[7:0]
CH0_GAIN_ALL[23:16]
CH0_GAIN_ALL[15:8]
CH0_GAIN_ALL[7:0]
0x00
R/W
0x01F CH0_GAIN_
UPPER_BYTE
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
0x020 CH0_GAIN_
MID_BYTE
0x021 CH0_GAIN_
LOWER_BYTE
0x022 CH1_OFFSET_
UPPER_BYTE
CH1_OFFSET_ALL[23:16]
CH1_OFFSET_ALL[15:8]
CH1_OFFSET_ALL[7:0]
CH1_GAIN_ALL[23:16]
CH1_GAIN_ALL[15:8]
CH1_GAIN_ALL[7:0]
0x023 CH1_OFFSET_
MID_BYTE
0x024 CH1_OFFSET_
LOWER_BYTE
0x025 CH1_GAIN_
UPPER_BYTE
0x026 CH1_GAIN_
MID_BYTE
0x027 CH1_GAIN_
LOWER_BYTE
0x028 CH2_OFFSET_
UPPER_BYTE
CH2_OFFSET_ALL[23:16]
CH2_OFFSET_ALL[15:8]
CH2_OFFSET_ALL[7:0]
CH2_GAIN_ALL[23:16]
CH2_GAIN_ALL[15:8]
CH2_GAIN_ALL[7:0]
0x029 CH2_OFFSET_
MID_BYTE
0x02A CH2_OFFSET_
LOWER_BYTE
0x02B CH2_GAIN_
UPPER_BYTE
0x02C CH2_GAIN_
MID_BYTE
0x02D CH2_GAIN_
LOWER_BYTE
0x02E CH3_OFFSET_
UPPER_BYTE
CH3_OFFSET_ALL[23:16]
CH3_OFFSET_ALL[15:8]
CH3_OFFSET_ALL[7:0]
CH3_GAIN_ALL[23:16]
CH3_GAIN_ALL[15:8]
CH3_GAIN_ALL[7:0]
0x02F CH3_OFFSET_
MID_BYTE
0x030 CH3_OFFSET_
LOWER_BYTE
0x031 CH3_GAIN_
UPPER_BYTE
0x032 CH3_GAIN_
MID_BYTE
0x033 CH3_GAIN_
LOWER_BYTE
0x034 CH4_OFFSET_
UPPER_BYTE
CH4_OFFSET_ALL[23:16]
CH4_OFFSET_ALL[15:8]
CH4_OFFSET_ALL[7:0]
CH4_GAIN_ALL[23:16]
CH4_GAIN_ALL[15:8]
CH4_GAIN_ALL[7:0]
0x035 CH4_OFFSET_
MID_BYTE
0x036 CH4_OFFSET_
LOWER_BYTE
0x037 CH4_GAIN_
UPPER_BYTE
0x038 CH4_GAIN_
MID_BYTE
0x039 CH4_GAIN_
LOWER_BYTE
0x03A CH5_OFFSET_
UPPER_BYTE
CH5_OFFSET_ALL[23:16]
CH5_OFFSET_ALL[15:8]
CH5_OFFSET_ALL[7:0]
CH5_GAIN_ALL[23:16]
CH5_GAIN_ALL[15:8]
0x03B CH5_OFFSET_
MID_BYTE
0x03C CH5_OFFSET_
LOWER_BYTE
0x03D CH5_GAIN_
UPPER_BYTE
0x03E CH5_GAIN_
MID_BYTE
Rev. 0 | Page 62 of 98
Data Sheet
AD7771
Reg.
Name
Bits
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset
R/W
0x03F CH5_GAIN_
LOWER_BYTE
[7:0]
CH5_GAIN_ALL[7:0]
0x00
R/W
0x040 CH6_OFFSET_
UPPER_BYTE
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
CH6_OFFSET_ALL[23:16]
CH6_OFFSET_ALL[15:8]
CH6_OFFSET_ALL[7:0]
CH6_GAIN_ALL[23:16]
CH6_GAIN_ALL[15:8]
CH6_GAIN_ALL[7:0]
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
0x00
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R
0x041 CH6_OFFSET_
MID_BYTE
0x042 CH6_OFFSET_
LOWER_BYTE
0x043 CH6_GAIN_
UPPER_BYTE
0x044 CH6_GAIN_
MID_BYTE
0x045 CH6_GAIN_
LOWER_BYTE
0x046 CH7_OFFSET_
UPPER_BYTE
CH7_OFFSET_ALL[23:16]
CH7_OFFSET_ALL[15:8]
CH7_OFFSET_ALL[7:0]
CH7_GAIN_ALL[23:16]
CH7_GAIN_ALL[15:8]
CH7_GAIN_ALL[7:0]
0x047 CH7_OFFSET_
MID_BYTE
0x048 CH7_OFFSET_
LOWER_BYTE
0x049 CH7_GAIN_
UPPER_BYTE
0x04A CH7_GAIN_
MID_BYTE
0x04B CH7_GAIN_
LOWER_BYTE
0x04C CH0_ERR_REG
0x04D CH1_ERR_REG
0x04E CH2_ERR_REG
0x04F CH3_ERR_REG
0x050 CH4_ERR_REG
0x051 CH5_ERR_REG
0x052 CH6_ERR_REG
0x053 CH7_ERR_REG
RESERVED
CH0_ERR_
AINM_UV
CH0_ERR_ CH0_ERR_
AINM_OV AINP_UV
CH1_ERR_ CH1_ERR_
AINM_OV AINP_UV
CH2_ERR_ CH2_ERR_
AINM_OV AINP_UV
CH3_ERR_ CH3_ERR_
AINM_OV AINP_UV
CH4_ERR_ CH4_ERR_
AINM_OV AINP_UV
CH5_ERR_ CH5_ERR_
AINM_OV AINP_UV
CH6_ERR_ CH6_ERR_
AINM_OV AINP_UV
CH7_ERR_ CH7_ERR_
AINM_OV AINP_UV
CH1_ERR_ CH0_ERR_
CH0_ERR_
AINP_OV
CH0_ERR_
REF_DET
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
CH1_ERR_
AINM_UV
CH1_ERR_
AINP_OV
CH1_ERR_
REF_DET
R
CH2_ERR_
AINM_UV
CH2_ERR_
AINP_OV
CH2_ERR_
REF_DET
R
CH3_ERR_
AINM_UV
CH3_ERR_
AINP_OV
CH3_ERR_
REF_DET
R
CH4_ERR_
AINM_UV
CH4_ERR_AI CH4_ERR_
NP_OV
R
REF_DET
CH5_ERR_
AINM_UV
CH5_ERR_
AINP_OV
CH5_ERR_
REF_DET
R
CH6_ERR_
AINM_UV
CH6_ERR_
AINP_OV
CH6_ERR_
REF_DET
R
CH7_ERR_
AINM_UV
CH7_ERR_
AINP_OV
CH7_ERR_
REF_DET
R
0x054 CH0_1_SAT_
ERR
RESERVED
CH1_ERR_
MOD_SAT
CH1_ERR_
CH0_ERR_
FILTER_SAT
CH0_ERR_
OUTPUT_
SAT
R
FILTER_SAT
OUTPUT_
SAT
MOD_SAT
0x055 CH2_3_SAT_
ERR
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
RESERVED
RESERVED
RESERVED
CH3_ERR_
MOD_SAT
CH3_ERR_
FILTER_SAT
CH3_ERR_ CH2_ERR_
CH2_ERR_
FILTER_SAT
CH2_ERR_
OUTPUT_
SAT
0x00
0x00
0x00
0xFE
0x00
0x3E
R
OUTPUT_
SAT
MOD_SAT
0x056 CH4_5_SAT_
ERR
CH5_ERR_
MOD_SAT
CH5_ERR_
FILTER_SAT
CH5_ERR_ CH4_ERR_
CH4_ERR_
FILTER_SAT
CH4_ERR_
OUTPUT_
SAT
R
OUTPUT_
SAT
MOD_SAT
0x057 CH6_7_SAT_
ERR
CH7_ERR_
MOD_SAT
CH7_ERR_
FILTER_SAT
CH7_ERR_ CH6_ERR_
CH6_ERR_
FILTER_SAT
CH6_ERR_
OUTPUT_
SAT
R
OUTPUT_
SAT
MOD_SAT
0x058 CHX_ERR_
REG_EN
OUTPUT_ FILTER_
MOD_SAT_
TEST_EN
AINM_UV_
TEST_EN
AINM_OV_ AINP_UV_
AINP_OV_
TEST_EN
REF_DET_
TEST_EN
R/W
R
SAT_
SAT_
TEST_EN
TEST_EN
TEST_EN
TEST_EN
0x059 GEN_ERR_
REG_1
RESERVED
MEMMAP_
CRC_ERR
ROM_CRC_
ERR
SPI_CLK_
COUNT_
ERR
SPI_
INVALID_
READ_ERR
SPI_
INVALID_
WRITE_ERR
SPI_CRC_
ERR
0x05A GEN_ERR_
REG_1_EN
RESERVED
MEMMAP_
CRC_TEST_EN
ROM_CRC_
TEST_EN
SPI_CLK_
COUNT_
TEST_EN
SPI_
SPI_
SPI_CRC_
TEST_EN
R/W
INVALID_
READ_
TEST_EN
INVALID_
WRITE_
TEST_EN
0x05B GEN_ERR_
REG_2
[7:0]
[7:0]
RESERVED
RESERVED
RESET_
DETECTED
EXT_MCLK_
SWITCH_ERR
RESERVED ALDO1_
PSM_ERR
ALDO2_
PSM_ERR
DLDO_
PSM_ERR
0x00
0x3C
R
0x05C GEN_ERR_
REG_2_EN
RESET_
DETECT_EN
RESERVED
LDO_PSM_TEST_EN
LDO_PSM_TRIP_TEST_EN
R/W
Rev. 0 | Page 63 of 98
AD7771
Data Sheet
Reg.
Name
Bits
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
ERR_LOC_ ERR_LOC_
CH3 CH2
ERR_LOC_ ERR_LOC_
GEN1 CH7
Bit 2
Bit 1
Bit 0
Reset
R/W
0x05D STATUS_REG_1
0x05E STATUS_REG_2
0x05F STATUS_REG_3
[7:0]
RESERVED
CHIP_ERROR
ERR_LOC_
CH4
ERR_LOC_
CH1
ERR_LOC_C 0x00
H0
R
[7:0]
[7:0]
RESERVED
RESERVED
CHIP_ERROR
CHIP_ERROR
ERR_LOC_
GEN2
ERR_LOC_
CH6
ERR_LOC_C 0x00
H5
R
R
INIT_
ERR_LOC_ ERR_LOC_
ERR_LOC_
ERR_LOC_
0x00
COMPLETE
SAT_CH6_ SAT_CH4_5
7
SAT_CH2_3
SAT_CH0_1
0x060 SRC_N_MSB
0x061 SRC_N_LSB
0x062 SRC_IF_MSB
0x063 SRC_IF_LSB
0x064 SRC_UPDATE
[7:0]
[7:0]
[7:0]
[7:0]
[7:0]
RESERVED
SRC_N_ALL[11:8]
0x00
0x80
0x00
0x00
R/W
R/W
R/W
R/W
R/W
SRC_N_ALL[7:0]
SRC_IF_ALL[15:8]
SRC_IF_ALL[7:0]
RESERVED
SRC_
LOAD_
SRC_LOAD_ 0x00
UPDATE
SOURCE
Rev. 0 | Page 64 of 98
Data Sheet
AD7771
REGISTER DETAILS
CHANNEL 0 CONFIGURATION REGISTER
Address: 0x000, Reset: 0x00, Name: CH0_CONFIG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] CH0_GAIN (R/W)
AFE Gain
00: Gain 1.
01: Gain 2.
10: Gain 4.
11: Gain 8.
[2:0] RESERVED
[3] RESERVED
[5] CH0_REF_MONITOR (R/W)
Channel used as Reference monitor
[4] CH0_RX (R/W)
Channel Meter Mux RX Mode
Table 44. Bit Descriptions for CH0_CONFIG
Bits Bit Name
Settings Description
Reset Access
[7:6] CH0_GAIN
AFE Gain
0x0
R/W
00 Gain = 1
01 Gain = 2
10 Gain = 4
11 Gain = 8
5
4
CH0_REF_MONITOR
CH0_RX
Channel Used as Reference Monitor
Channel Meter Mux Rx Mode
Reserved
0x0
0x0
0x0
R/W
R/W
R/W
[3:0] RESERVED
CHANNEL 1 CONFIGURATION REGISTER
Address: 0x001, Reset: 0x00, Name: CH1_CONFIG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] CH1_GAIN (R/W)
AFE Gain
00: Gain = 1.
01: Gain = 2.
10: Gain = 4.
11: Gain = 8.
[2:0] RESERVED
[3] RESERVED
[5] CH1_REF_MONITOR (R/W)
Channel used as Reference monitor
[4] CH1_RX (R/W)
Channel Meter Mux RX Mode
Table 45. Bit Descriptions for CH1_CONFIG
Bits Bit Name
Settings Description
Reset Access
[7:6] CH1_GAIN
AFE Gain
0x0
R/W
00 Gain = 1
01 Gain = 2
10 Gain = 4
11 Gain = 8
5
4
CH1_REF_MONITOR
CH1_RX
Channel Used as Reference Monitor
Channel Meter Mux Rx Mode
Reserved
0x0
0x0
0x0
R/W
R/W
R/W
[3:0] RESERVED
Rev. 0 | Page 65 of 98
AD7771
Data Sheet
CHANNEL 2 CONFIGURATION REGISTER
Address: 0x002, Reset: 0x00, Name: CH2_CONFIG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] CH2_GAIN (R/W)
AFE Gain
00: Gain 1.
01: Gain 2.
10: Gain 4.
11: Gain 8.
[2:0] RESERVED
[3] RESERVED
[5] CH2_REF_MONITOR (R/W)
Channel used as Reference monitor
[4] CH2_RX (R/W)
Channel Meter Mux RX Mode
Table 46. Bit Descriptions for CH2_CONFIG
Bits Bit Name
Settings Description
Reset Access
[7:6] CH2_GAIN
AFE Gain
0x0
R/W
00 Gain = 1
01 Gain = 2
10 Gain = 4
11 Gain = 8
5
4
CH2_REF_MONITOR
CH2_RX
Channel Used as Reference Monitor
Channel Meter Mux Rx Mode
Reserved
0x0
0x0
0x0
R/W
R/W
R/W
[3:0] RESERVED
CHANNEL 3 CONFIGURATION REGISTER
Address: 0x003, Reset: 0x00, Name: CH3_CONFIG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] CH3_GAIN (R/W)
AFE Gain
00: Gain 1.
01: Gain 2.
10: Gain 4.
11: Gain 8.
[2:0] RESERVED
[3] RESERVED
[5] CH3_REF_MONITOR (R/W)
Channel used as Reference monitor
[4] CH3_RX (R/W)
Channel Meter Mux RX Mode
Table 47. Bit Descriptions for CH3_CONFIG
Bits Bit Name
Settings Description
Reset Access
[7:6] CH3_GAIN
AFE Gain
0x0
R/W
00 Gain = 1
01 Gain = 2
10 Gain = 4
11 Gain = 8
5
4
CH3_REF_MONITOR
CH3_RX
Channel Used as Reference Monitor
Channel Meter Mux Rx Mode
Reserved
0x0
0x0
0x0
R/W
R/W
R/W
[3:0] RESERVED
Rev. 0 | Page 66 of 98
Data Sheet
AD7771
CHANNEL 4 CONFIGURATION REGISTER
Address: 0x004, Reset: 0x00, Name: CH4_CONFIG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] CH4_GAIN (R/W)
AFE Gain
00: Gain 1.
01: Gain 2.
10: Gain 4.
11: Gain 8.
[2:0] RESERVED
[3] RESERVED
[5] CH4_REF_MONITOR (R/W)
Channel used as Reference monitor
[4] CH4_RX (R/W)
Channel Meter Mux RX Mode
Table 48. Bit Descriptions for CH4_CONFIG
Bits Bit Name
Settings Description
Reset Access
[7:6] CH4_GAIN
AFE Gain
0x0
R/W
00 Gain = 1
01 Gain = 2
10 Gain = 4
11 Gain = 8
5
4
CH4_REF_MONITOR
CH4_RX
Channel Used as Reference Monitor
Channel Meter Mux Rx Mode
Reserved
0x0
0x0
0x0
R/W
R/W
R/W
[3:0] RESERVED
CHANNEL 5 CONFIGURATION REGISTER
Address: 0x005, Reset: 0x00, Name: CH5_CONFIG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] CH5_GAIN (R/W)
AFE Gain
00: Gain 1.
01: Gain 2.
10: Gain 4.
11: Gain 8.
[2:0] RESERVED
[3] RESERVED
[5] CH5_REF_MONITOR (R/W)
Channel used as Reference monitor
[4] CH5_RX (R/W)
Channel Meter Mux RX Mode
Table 49. Bit Descriptions for CH5_CONFIG
Bits Bit Name
Settings Description
Reset Access
[7:6] CH5_GAIN
AFE Gain
0x0
R/W
00 Gain = 1
01 Gain = 2
10 Gain = 4
11 Gain = 8
5
4
CH5_REF_MONITOR
CH5_RX
Channel Used as Reference Monitor
Channel Meter Mux Rx Mode
Reserved
0x0
0x0
0x0
R/W
R/W
R/W
[3:0] RESERVED
Rev. 0 | Page 67 of 98
AD7771
Data Sheet
CHANNEL 6 CONFIGURATION REGISTER
Address: 0x006, Reset: 0x00, Name: CH6_CONFIG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] CH6_GAIN (R/W)
AFE Gain
00: Gain 1.
01: Gain 2.
10: Gain 4.
11: Gain 8.
[2:0] RESERVED
[3] RESERVED
[5] CH6_REF_MONITOR (R/W)
Channel used as Reference monitor
[4] CH6_RX (R/W)
Channel Meter Mux RX Mode
Table 50. Bit Descriptions for CH6_CONFIG
Bits Bit Name
Settings Description
Reset Access
[7:6] CH6_GAIN
AFE Gain
0x0
R/W
00 Gain = 1
01 Gain = 2
10 Gain = 4
11 Gain = 8
5
4
CH6_REF_MONITOR
CH6_RX
Channel Used as Reference Monitor
Channel Meter Mux Rx Mode
Reserved
0x0
0x0
0x0
R/W
R/W
R/W
[3:0] RESERVED
CHANNEL 7 CONFIGURATION REGISTER
Address: 0x007, Reset: 0x00, Name: CH7_CONFIG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] CH7_GAIN (R/W)
AFE Gain
00: Gain 1.
01: Gain 2.
10: Gain 4.
11: Gain 8.
[2:0] RESERVED
[3] RESERVED
[5] CH7_REF_MONITOR (R/W)
Channel used as Reference monitor
[4] CH7_RX (R/W)
Channel Meter Mux RX Mode
Table 51. Bit Descriptions for CH7_CONFIG
Bits Bit Name
Settings Description
Reset Access
[7:6] CH7_GAIN
AFE Gain
0x0
R/W
00 Gain = 1
01 Gain = 2
10 Gain = 4
11 Gain = 8
5
4
CH7_REF_MONITOR
CH7_RX
Channel Used as Reference Monitor
Channel Meter Mux Rx Mode
Reserved
0x0
0x0
0x0
R/W
R/W
R/W
[3:0] RESERVED
Rev. 0 | Page 68 of 98
Data Sheet
AD7771
DISABLE CLOCKS TO ADC CHANNEL REGISTER
Address: 0x008, Reset: 0x00, Name: CH_DISABLE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7] CH7_DISABLE (R/W)
[0] CH0_DISABLE (R/W)
Channel 7 Disable
Channel 0 Disable
[6] CH6_DISABLE (R/W)
[1] CH1_DISABLE (R/W)
Channel 6 Disable
Channel 1 Disable
[5] CH5_DISABLE (R/W)
[2] CH2_DISABLE (R/W)
Channel 5 Disable
Channel 2 Disable
[4] CH4_DISABLE (R/W)
[3] CH3_DISABLE (R/W)
Channel 4 Disable
Channel 3 Disable
Table 52. Bit Descriptions for CH_DISABLE
Bits
Bit Name
Settings
Description
Reset
0x0
0x0
0x0
0x0
0x0
0x0
0x0
0x0
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
7
6
5
4
3
2
1
0
CH7_DISABLE
CH6_DISABLE
CH5_DISABLE
CH4_DISABLE
CH3_DISABLE
CH2_DISABLE
CH1_DISABLE
CH0_DISABLE
Channel 7 Disable
Channel 6 Disable
Channel 5 Disable
Channel 4 Disable
Channel 3 Disable
Channel 2 Disable
Channel 1 Disable
Channel 0 Disable
CHANNEL 0 SYNC OFFSET REGISTER
Address: 0x009, Reset: 0x00, Name: CH0_SYNC_OFFSET
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH0_SYNC_OFFSET (R/W)
Channel Sync Offset
Table 53. Bit Descriptions for CH0_SYNC_OFFSET
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH0_SYNC_OFFSET
Channel Sync Offset
0x0
R/W
CHANNEL 1 SYNC OFFSET REGISTER
Address: 0x00A, Reset: 0x00, Name: CH1_SYNC_OFFSET
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH1_SYNC_OFFSET (R/W)
Channel Sync Offset
Table 54. Bit Descriptions for CH1_SYNC_OFFSET
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH1_SYNC_OFFSET
Channel Sync Offset
0x0
R/W
CHANNEL 2 SYNC OFFSET REGISTER
Address: 0x00B, Reset: 0x00, Name: CH2_SYNC_OFFSET
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH2_SYNC_OFFSET (R/W)
Channel Sync Offset
Table 55. Bit Descriptions for CH2_SYNC_OFFSET
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH2_SYNC_OFFSET
Channel Sync Offset
0x0
R/W
Rev. 0 | Page 69 of 98
AD7771
Data Sheet
CHANNEL 3 SYNC OFFSET REGISTER
Address: 0x00C, Reset: 0x00, Name: CH3_SYNC_OFFSET
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH3_SYNC_OFFSET (R/W)
Channel Sync Offset
Table 56. Bit Descriptions for CH3_SYNC_OFFSET
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH3_SYNC_OFFSET
Channel Sync Offset
0x0
R/W
CHANNEL 4 SYNC OFFSET REGISTER
Address: 0x00D, Reset: 0x00, Name: CH4_SYNC_OFFSET
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH4_SYNC_OFFSET (R/W)
Channel Sync Offset
Table 57. Bit Descriptions for CH4_SYNC_OFFSET
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH4_SYNC_OFFSET
Channel Sync Offset
0x0
R/W
CHANNEL 5 SYNC OFFSET REGISTER
Address: 0x00E, Reset: 0x00, Name: CH5_SYNC_OFFSET
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH5_SYNC_OFFSET (R/W)
Channel Sync Offset
Table 58. Bit Descriptions for CH5_SYNC_OFFSET
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH5_SYNC_OFFSET
Channel Sync Offset
0x0
R/W
CHANNEL 6 SYNC OFFSET REGISTER
Address: 0x00F, Reset: 0x00, Name: CH6_SYNC_OFFSET
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH6_SYNC_OFFSET (R/W)
Channel Sync Offset
Table 59. Bit Descriptions for CH6_SYNC_OFFSET
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH6_SYNC_OFFSET
Channel Sync Offset
0x0
R/W
CHANNEL 7 SYNC OFFSET REGISTER
Address: 0x010, Reset: 0x00, Name: CH7_SYNC_OFFSET
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH7_SYNC_OFFSET (R/W)
Channel Sync Offset
Table 60. Bit Descriptions for CH7_SYNC_OFFSET
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH7_SYNC_OFFSET
Channel Sync Offset
0x0
R/W
Rev. 0 | Page 70 of 98
Data Sheet
AD7771
GENERAL USER CONFIGURATION 1 REGISTER
Address: 0x011, Reset: 0x24, Name: GENERAL_USER_CONFIG_1
7
6
5
4
3
2
1
0
0
0
1
0
0
1
0
0
[7] ALL_CH_DIS_MCLK_EN (R/W)
[1:0] SOFT_RESET (R/W)
Soft Reset
00: No Effect.
01: No Effect.
10: 2nd write.
11: 1st write.
If all SD channels are disabled, setting
this bit high allows DCLK to continue
toggling
[6] POWERMODE (R/W)
Power Mode
0: Low Power (1/4)
1: High Resolution.
[2] PDB_RC_OSC (R/W)
Power-Down signal for internal oscillator.
Active Low
[5] PDB_VCM (R/W)
Power-Down VCM Buffer. Active Low
[3] PDB_SAR (R/W)
Power-Down SAR. Active Low
[4] PDB_REFOUT_BUF (R/W)
Power-Down Internal Reference Output
Buffer. Active Low
Table 61. Bit Descriptions for GENERAL_USER_CONFIG_1
Bits Bit Name Settings Description
Reset
Access
7
ALL_CH_DIS_MCLK_EN
If all Σ-Δ channels are disabled, setting this bit high allows DCLK to
continue toggling.
0x0
R/W
6
POWERMODE
Power Mode.
0x0
R/W
0
1
Low power (1/4).
High resolution.
5
4
3
2
PDB_VCM
Power-Down VCM Buffer. Active low.
Power-Down Internal Reference Output Buffer. Active low.
Power-Down SAR. Active low.
Power-Down Signal for Internal Oscillator. Active low.
Soft Reset
0x1
0x0
0x0
0x1
0x0
R/W
R/W
R/W
R/W
R/W
PDB_REFOUT_BUF
PDB_SAR
PDB_RC_OSC
[1:0] SOFT_RESET
00 No effect
01 No effect
10 2nd write
11 1st write
Rev. 0 | Page 71 of 98
AD7771
Data Sheet
GENERAL USER CONFIGURATION 2 REGISTER
Address: 0x012, Reset: 0x09, Name: GENERAL_USER_CONFIG_2
7
6
5
4
3
2
1
0
0
0
0
0
1
0
0
1
[7] RESERVED
[0] SPI_SYNC (R/W)
SYNC pulse generated thru SPI
0: This signal is ANDed with the value
on STARTb pin in the control module,
generate a pulse in /SYNC_IN pin.
1: This bit is ANDed with the value on
STARTb pin in the control module.
[6] FILTER_MODE (R/W)
0=Sinc3. 1=Sinc5
[5] SAR_DIAG_MODE_EN (R/W)
Sets SPI interface to read back SAR
result on SDO
[2:1] DOUT_DRIVE_STR (R/W)
DOUT Drive Strength
00: Nominal.
01: Strong.
10: Weak.
11: Extra Strong.
[4:3] SDO_DRIVE_STR (R/W)
SDO Drive Strength
00: Nominal.
01: Strong.
10: Weak.
11: Extra Strong.
Table 62. Bit Descriptions for GENERAL_USER_CONFIG_2
Bits Bit Name
Settings Description
Reset Access
7
6
5
RESERVED
FILTER_MODE
SAR_DIAG_MODE_EN
Reserved.
0 = Sinc3. 1 = Sinc5.
Sets SPI interface to read back SAR result on SDO.
SDO Drive Strength.
0x0
0x0
0x0
0x1
R/W
R/W
R/W
R/W
[4:3] SDO_DRIVE_STR
00
01
10
11
Nominal.
Strong.
Weak.
Extra Strong.
[2:1] DOUT_DRIVE_STR
DOUTx Drive Strength.
Nominal.
Strong.
Weak.
Extra Strong.
Sync pulse generated through SPI.
0x0
0x1
R/W
R/W
00
01
10
11
0
SPI_SYNC
0
1
This signal is AND’ed with the value on START pin in the control module to
generate a pulse in SYNC_IN pin.
This bit is AND’ed with the value on START pin in the control module.
Rev. 0 | Page 72 of 98
Data Sheet
AD7771
GENERAL USER CONFIGURATION 3 REGISTER
Address: 0x013, Reset: 0x80, Name: GENERAL_USER_CONFIG_3
7
6
5
4
3
2
1
0
1
0
0
0
0
0
0
0
[7:6] CONVST_DEGLITCH_DIS (R/W)
Disable deglitching of CONVST_SAR
pin
[0] CLK_QUAL_DIS (R/W)
Disables the clock qualifier check
if the user requires to use an MCLK
signal < 265kHz.
00: Reserved.
01: Reserved.
10: CONVST_SAR Deglitch 1.5/ MCLK.
11: No deglitch circuit.
[3:1] RESERVED
[5] RESERVED
[4] SPI_SLAVE_MODE_EN (R/W)
Enable to SPI slave mode to read
back ADC on SDO
Table 63. Bit Descriptions for GENERAL_USER_CONFIG_3
Bits Bit Name
Settings Description
Reset
Access
[7:6] CONVST_DEGLITCH_DIS
Disable deglitching of CONVST_SAR pin.
0x2
R/W
00
01
10
11
Reserved.
Reserved.
CONVST_SAR deglitch 1.5/MCLK.
No deglitch circuit.
5
4
RESERVED
Reserved.
0x0
0x0
0x0
0x0
0x0
R/W
R/W
R/W
R/W
R/W
SPI_SLAVE_MODE_EN
Enable to SPI slave mode to read back ADC on SDO.
[3:2] RESERVED
Reserved.
Reserved.
1
0
RESERVED
CLK_QUAL_DIS
Disables the clock qualifier check if the user requires to use an MCLK
signal <265 kHz.
DATA OUTPUT FORMAT REGISTER
Address: 0x014, Reset: 0x20, Name: DOUT_FORMAT
7
6
5
4
3
2
1
0
0
0
1
0
0
0
0
0
[7:6] DOUT_FORMAT (R/W)
Data out format
00: 4 DOUT Lines.
01: 2 DOUT Lines.
10: 1 DOUT Lines.
11: 1 DOUT Lines.
[0] RESERVED
[3:1] DCLK_CLK_DIV (R/W)
Divide MCLK
000: Divide by 1.
001: Divide by 2.
010: Divide by 4.
011: Divide by 8.
100: Divide by 16.
101: Divide by 32.
110: Divide by 64.
111: Divide by 128.
[5] DOUT_HEADER_FORMAT (R/W)
Dout header format
0: Status Header.
1: CRC Header.
[4] RESERVED
Table 64. Bit Descriptions for DOUT_FORMAT
Bits Bit Name
Settings Description
Reset
Access
[7:6] DOUT_FORMAT
Data Out Format
0x0
R/W
00 4 DOUTx lines
01 2 DOUTx lines
10 1 DOUTx lines
11 1 DOUTx line
5
4
DOUT_HEADER_FORMAT
DOUTx Header Format
Status header
CRC header
0x1
0x0
R/W
R/W
0
1
RESERVED
Reserved
Rev. 0 | Page 73 of 98
AD7771
Data Sheet
Bits Bit Name
Settings Description
Divide MCLK
Reset
Access
[3:1] DCLK_CLK_DIV
0x0
R/W
000 Divide by 1
001 Divide by 2
010 Divide by 4
011 Divide by 8
100 Divide by 16
101 Divide by 32
110 Divide by 64
111 Divide by 128
Reserved
0
RESERVED
0x0
R/W
MAIN ADC METER AND REFERENCE MUX CONTROL REGISTER
Address: 0x015, Reset: 0x00, Name: ADC_MUX_CONFIG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] REF_MUX_CTRL (R/W)
[1:0] RESERVED
SD ADC Reference Mux
00: External Reference REFx+/REFx-
01: Internal Reference.
10: External Supply AVDD1x/AVSSx.
11: External Reference REFx-/REFx+.
[5:2] MTR_MUX_CTRL (R/W)
SD ADC Meter Mux
0010: 280mV.
0011: External Reference REFx+/REFx-
0100: External Reference REFx-/REFx+.
0101: External Reference REFx-/REFx-
0110: Internal Reference +/-
0111: Internal Reference -/+.
1000: Internal Reference +/+.
1001: External Reference REFx+/REFx+.
Table 65. Bit Descriptions for ADC_MUX_CONFIG
Bits
Bit Name
Settings
Description
Reset
Access
[7:6]
REF_MUX_CTRL
Σ-Δ ADC Reference Mux.
0x0
R/W
00 External reference REFx+/REFx−.
01 Internal reference.
10 External supply AVDD1x/AVSSx.
11 External reference REFx−/REFx+.
Σ-Δ ADC Meter Mux.
[5:2]
MTR_MUX_CTRL
0x0
R/W
0010 280 mV.
0011 External reference REFx+/REFx−.
0100 External reference REFx−/REFx+.
0101 External reference REFx−/REFx−.
0110 Internal reference +/−.
0111 Internal reference −/+.
1000 Internal reference +/+.
1001 External reference REFx+/REFx+.
Reserved.
[1:0]
RESERVED
0x0
R/W
Rev. 0 | Page 74 of 98
Data Sheet
AD7771
GLOBAL DIAGNOSTICS MUX REGISTER
Address: 0x016, Reset: 0x00, Name: GLOBAL_MUX_CONFIG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:3] GLOBAL_MUX_CTRL (R/W)
[2:0] RESERVED
Global SAR diagnostics mux control
00000: AUXAin+ AUXAin-
00001: DVBE AVSSx.
00010: REF1P REF1N.
...
10011: REF1+ AVSSx.
10100: REF2+ AVSSx.
10101: AVSSx AVDD4. Attenuated.
Table 66. Bit Descriptions for GLOBAL_MUX_CONFIG
Bits Bit Name Settings Description
[7:3] GLOBAL_MUX_CTRL Global SAR Diagnostics Mux Control.
00000 AUXAIN+/AUXAIN−.
Reset
Access
0x0
R/W
00001 DVBE/AVSSx.
00010 REF1+/REF1−.
10011 REF2+/REF2−.
10100 REF_OUT/AVSSx.
10101 VCM/AVSSx.
10110 AREG1CAP/AVSSx.
10111 AREG2CAP/AVSSx.
11000 DREGCAP/DGND.
11001 AVDD1A/AVSSx.
11010 AVDD1B/AVSSx.
11011 AVDD2A/AVSSx.
11100 AVDD2B/AVSSx.
11101 IOVDD/DGND.
11110 AVDD4/AVSSx.
11111 DGND/AVSSx.
10000 DGND/AVSSx.
10001 DGND/AVSSx.
10010 AVDD4/AVSSx.
10011 REF1+/AVSSx.
10100 REF2+/AVSSx.
10101 AVSSx/AVDD4. Attenuated.
Reserved.
[2:0] RESERVED
0x0
R/W
GPIO CONFIGURATION REGISTER
Address: 0x017, Reset: 0x00, Name: GPIO_CONFIG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:3] RESERVED
[2:0] GPIO_OP_EN (R/W)
GPIO input/output
Table 67. Bit Descriptions for GPIO_CONFIG
Bits Bit Name
[7:3] RESERVED
[2:0] GPIO_OP_EN
Settings Description
Reset Access
Reserved.
0x0
0x0
R/W
R/W
GPIO Input/Output
Rev. 0 | Page 75 of 98
AD7771
Data Sheet
GPIO DATA REGISTER
Address: 0x018, Reset: 0x00, Name: GPIO_DATA
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] RESERVED
[2:0] GPIO_WRITE_DATA (R/W)
Value sent to GPIO pins
[5:3] GPIO_READ_DATA (R)
Data read from GPIO pins
Table 68. Bit Descriptions for GPIO_DATA
Bits Bit Name
Settings Description
Reset Access
[7:6] RESERVED
[5:3] GPIO_READ_DATA
[2:0] GPIO_WRITE_DATA
Reserved.
Data Read from the GPIO Pins
Value Sent to the GPIO Pins
0x0
0x0
0x0
R/W
R
R/W
BUFFER CONFIGURATION 1 REGISTER
Address: 0x019, Reset: 0x38, Name: BUFFER_CONFIG_1
7
6
5
4
3
2
1
0
0
0
0
1
1
0
0
0
[7] RESERVED
[0] RESERVED
[1] RESERVED
[2] RESERVED
[6] RESERVED
[5] RESERVED
[4] REF_BUF_POS_EN (R/W)
[3] REF_BUF_NEG_EN (R/W)
Reference buffer positive enable
Reference buffer negative enable
Table 69. Bit Descriptions for BUFFER_CONFIG_1
Bits
[7:5]
4
3
[2:0]
Bit Name
Settings
Description
Reset
0x0
0x1
0x1
0x0
Access
R/W
R/W
R/W
R/W
RESERVED
Reserved
REF_BUF_POS_EN
REF_BUF_NEG_EN
RESERVED
Reference Buffer Positive Enable
Reference Buffer Negative Enable
Reserved
BUFFER CONFIGURATION 2 REGISTER
Address: 0x01A, Reset: 0xC0, Name: BUFFER_CONFIG_2
7
6
5
4
3
2
1
0
1
1
0
0
0
0
0
0
[7] REFBUFP_PREQ (R/W)
Reference buffer positive precharge
enable
[0] PDB_DLDO_OVRDRV (R/W)
DRegCap Overdrive Enable.
[1] PDB_ALDO2_OVRDRV (R/W)
[6] REFBUFN_PREQ (R/W)
Reference buffer negative precharge
enable
AReg2Cap Overdrive Enable
[2] PDB_ALDO1_OVRDRV (R/W)
AReg1Cap Overdrive Enable
[5:3] RESERVED
Table 70. Bit Descriptions for BUFFER_CONFIG_2
Bits
Bit Name
Settings Description
Reset
0x1
0x1
0x0
0x0
0x0
0x0
Access
R/W
R/W
R/W
R/W
R/W
R/W
7
6
REFBUFP_PREQ
REFBUFN_PREQ
Reference Buffer Positive Precharge Enable
Reference Buffer Negative Precharge Enable
Reserved
AREG1CAP Overdrive Enable
AREG2CAP Overdrive Enable
DREGCAP Overdrive Enable
[5:3] RESERVED
2
1
0
PDB_ALDO1_OVRDRV
PDB_ALDO2_OVRDRV
PDB_DLDO_OVRDRV
Rev. 0 | Page 76 of 98
Data Sheet
AD7771
CHANNEL 0 OFFSET UPPER BYTE REGISTER
Address: 0x01C, Reset: 0x00, Name: CH0_OFFSET_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH0_OFFSET_ALL[23:16] (R/W)
Combined Offset register Channel 0
Table 71. Bit Descriptions for CH0_OFFSET_UPPER_BYTE
Bits Bit Name
Settings Description
Reset
Access
[7:0] CH0_OFFSET_ALL[23:16]
Combined Offset Register Channel 0
0x0
R/W
CHANNEL 0 OFFSET MIDDLE BYTE REGISTER
Address: 0x01D, Reset: 0x00, Name: CH0_OFFSET_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH0_OFFSET_ALL[15:8] (R/W)
Combined Offset register Channel 0
Table 72. Bit Descriptions for CH0_OFFSET_MID_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH0_OFFSET_ALL[15:8]
Combined Offset Register Channel 0
0x0
R/W
CHANNEL 0 OFFSET LOWER BYTE REGISTER
Address: 0x01E, Reset: 0x00, Name: CH0_OFFSET_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH0_OFFSET_ALL[7:0] (R/W)
Combined Offset register Channel 0
Table 73. Bit Descriptions for CH0_OFFSET_LOWER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH0_OFFSET_ALL[7:0]
Combined Offset Register Channel 0
0x0
R/W
CHANNEL 0 GAIN UPPER BYTE REGISTER
Address: 0x01F, Reset: 0x00, Name: CH0_GAIN_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH0_GAIN_ALL[23:16] (R/W)
Combined gain register Channel 0
Table 74. Bit Descriptions for CH0_GAIN_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH0_GAIN_ALL[23:16]
Combined Gain Register Channel 0
0x0
R/W
CHANNEL 0 GAIN MIDDLE BYTE REGISTER
Address: 0x020, Reset: 0x00, Name: CH0_GAIN_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH0_GAIN_ALL[15:8] (R/W)
Combined gain register Channel 0
Table 75. Bit Descriptions for CH0_GAIN_MID_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0] CH0_GAIN_ALL[15:8]
Combined Gain Register Channel 0
0x0
R/W
Rev. 0 | Page 77 of 98
AD7771
Data Sheet
CHANNEL 0 GAIN LOWER BYTE REGISTER
Address: 0x021, Reset: 0x00, Name: CH0_GAIN_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH0_GAIN_ALL[7:0] (R/W)
Combined gain register Channel 0
Table 76. Bit Descriptions for CH0_GAIN_LOWER_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH0_GAIN_ALL[7:0]
Combined Gain Register Channel 0
0x0
R/W
CHANNEL 1 OFFSET UPPER BYTE REGISTER
Address: 0x022, Reset: 0x00, Name: CH1_OFFSET_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH1_OFFSET_ALL[23:16] (R/W)
Combined offset register Channel 1
Table 77. Bit Descriptions for CH1_OFFSET_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH1_OFFSET_ALL[23:16]
Combined Offset Register Channel 1
0x0
R/W
CHANNEL 1 OFFSET MIDDLE BYTE REGISTER
Address: 0x023, Reset: 0x00, Name: CH1_OFFSET_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH1_OFFSET_ALL[15:8] (R/W)
Combined offset register Channel 1
Table 78. Bit Descriptions for CH1_OFFSET_MID_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH1_OFFSET_ALL[15:8]
Combined Offset Register Channel 1
0x0
R/W
CHANNEL 1 OFFSET LOWER BYTE REGISTER
Address: 0x024, Reset: 0x00, Name: CH1_OFFSET_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH1_OFFSET_ALL[7:0] (R/W)
Combined offset register Channel 1
Table 79. Bit Descriptions for CH1_OFFSET_LOWER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH1_OFFSET_ALL[7:0]
Combined Offset Register Channel 1
0x0
R/W
CHANNEL 1 GAIN UPPER BYTE REGISTER
Address: 0x025, Reset: 0x00, Name: CH1_GAIN_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH1_GAIN_ALL[23:16] (R/W)
Combined gain register Channel 1
Table 80. Bit Descriptions for CH1_GAIN_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH1_GAIN_ALL[23:16]
Combined Gain Register Channel 1
0x0
R/W
Rev. 0 | Page 78 of 98
Data Sheet
AD7771
CHANNEL 1 GAIN MIDDLE BYTE REGISTER
Address: 0x026, Reset: 0x00, Name: CH1_GAIN_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH1_GAIN_ALL[15:8] (R/W)
Combined gain register Channel 1
Table 81. Bit Descriptions for CH1_GAIN_MID_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0] CH1_GAIN_ALL[15:8]
Combined Gain Register Channel 1
0x0
R/W
CHANNEL 1 GAIN LOWER BYTE REGISTER
Address: 0x027, Reset: 0x00, Name: CH1_GAIN_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH1_GAIN_ALL[7:0] (R/W)
Combined gain register Channel 1
Table 82. Bit Descriptions for CH1_GAIN_LOWER_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH1_GAIN_ALL[7:0]
Combined Gain Register Channel 1
0x0
R/W
CHANNEL 2 OFFSET UPPER BYTE REGISTER
Address: 0x028, Reset: 0x00, Name: CH2_OFFSET_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH2_OFFSET_ALL[23:16] (R/W)
Combined offset register Channel 2
Table 83. Bit Descriptions for CH2_OFFSET_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH2_OFFSET_ALL[23:16]
Combined Offset Register Channel 2
0x0
R/W
CHANNEL 2 OFFSET MIDDLE BYTE REGISTER
Address: 0x029, Reset: 0x00, Name: CH2_OFFSET_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH2_OFFSET_ALL[15:8] (R/W)
Combined offset register Channel 2
Table 84. Bit Descriptions for CH2_OFFSET_MID_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH2_OFFSET_ALL[15:8]
Combined Offset Register Channel 2
0x0
R/W
CHANNEL 2 OFFSET LOWER BYTE REGISTER
Address: 0x02A, Reset: 0x00, Name: CH2_OFFSET_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH2_OFFSET_ALL[7:0] (R/W)
Combined offset register Channel 2
Table 85. Bit Descriptions for CH2_OFFSET_LOWER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH2_OFFSET_ALL[7:0]
Combined Offset Register Channel 2
0x0
R/W
Rev. 0 | Page 79 of 98
AD7771
Data Sheet
CHANNEL 2 GAIN UPPER BYTE REGISTER
Address: 0x02B, Reset: 0x00, Name: CH2_GAIN_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH2_GAIN_ALL[23:16] (R/W)
Combined gain register Channel 2
Table 86. Bit Descriptions for CH2_GAIN_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH2_GAIN_ALL[23:16]
Combined Gain Register Channel 2
0x0
R/W
CHANNEL 2 GAIN MIDDLE BYTE REGISTER
Address: 0x02C, Reset: 0x00, Name: CH2_GAIN_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH2_GAIN_ALL[15:8] (R/W)
Combined gain register Channel 2
Table 87. Bit Descriptions for CH2_GAIN_MID_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0] CH2_GAIN_ALL[15:8]
Combined Gain Register Channel 2
0x0
R/W
CHANNEL 2 GAIN LOWER BYTE REGISTER
Address: 0x02D, Reset: 0x00, Name: CH2_GAIN_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH2_GAIN_ALL[7:0] (R/W)
Combined gain register Channel 2
Table 88. Bit Descriptions for CH2_GAIN_LOWER_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH2_GAIN_ALL[7:0]
Combined Gain Register Channel 2
0x0
R/W
CHANNEL 3 OFFSET UPPER BYTE REGISTER
Address: 0x02E, Reset: 0x00, Name: CH3_OFFSET_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH3_OFFSET_ALL[23:16] (R/W)
Combined offset register Channel 3
Table 89. Bit descriptions for CH3_OFFSET_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH3_OFFSET_ALL[23:16]
Combined Offset Register Channel 3
0x0
R/W
CHANNEL 3 OFFSET MIDDLE BYTE REGISTER
Address: 0x02F, Reset: 0x00, Name: CH3_OFFSET_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH3_OFFSET_ALL[15:8] (R/W)
Combined offset register Channel 3
Table 90. Bit Descriptions for CH3_OFFSET_MID_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH3_OFFSET_ALL[15:8]
Combined Offset Register Channel 3
0x0
R/W
Rev. 0 | Page 80 of 98
Data Sheet
AD7771
CHANNEL 3 OFFSET LOWER BYTE REGISTER
Address: 0x030, Reset: 0x00, Name: CH3_OFFSET_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH3_OFFSET_ALL[7:0] (R/W)
Combined offset register Channel 3
Table 91. Bit Descriptions for CH3_OFFSET_LOWER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH3_OFFSET_ALL[7:0]
Combined Offset Register Channel 3
0x0
R/W
CHANNEL 3 GAIN UPPER BYTE REGISTER
Address: 0x031, Reset: 0x00, Name: CH3_GAIN_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH3_GAIN_ALL[23:16] (R/W)
Combined gain register Channel 3
Table 92. Bit Descriptions for CH3_GAIN_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH3_GAIN_ALL[23:16]
Combined Gain Register Channel 3
0x0
R/W
CHANNEL 3 GAIN MIDDLE BYTE REGISTER
Address: 0x032, Reset: 0x00, Name: CH3_GAIN_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH3_GAIN_ALL[15:8] (R/W)
Combined gain register Channel 3
Table 93. Bit Descriptions for CH3_GAIN_MID_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0] CH3_GAIN_ALL[15:8]
Combined Gain Register Channel 3
0x0
R/W
CHANNEL 3 GAIN LOWER BYTE REGISTER
Address: 0x033, Reset: 0x00, Name: CH3_GAIN_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH3_GAIN_ALL[7:0] (R/W)
Combined gain register Channel 3
Table 94. Bit Descriptions for CH3_GAIN_LOWER_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH3_GAIN_ALL[7:0]
Combined Gain Register Channel 3
0x0
R/W
CHANNEL 4 OFFSET UPPER BYTE REGISTER
Address: 0x034, Reset: 0x00, Name: CH4_OFFSET_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH4_OFFSET_ALL[23:16] (R/W)
Combined offset register Channel 4
Table 95. Bit Descriptions for CH4_OFFSET_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH4_OFFSET_ALL[23:16]
Combined Offset Register Channel 4
0x0
R/W
Rev. 0 | Page 81 of 98
AD7771
Data Sheet
CHANNEL 4 OFFSET MIDDLE BYTE REGISTER
Address: 0x035, Reset: 0x00, Name: CH4_OFFSET_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH4_OFFSET_ALL[15:8] (R/W)
Combined offset register Channel 4
Table 96. Bit Descriptions for CH4_OFFSET_MID_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH4_OFFSET_ALL[15:8]
Combined Offset Register Channel 4
0x0
R/W
CHANNEL 4 OFFSET LOWER BYTE REGISTER
Address: 0x036, Reset: 0x00, Name: CH4_OFFSET_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH4_OFFSET_ALL[7:0] (R/W)
Combined offset register Channel 4
Table 97. Bit Descriptions for CH4_OFFSET_LOWER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH4_OFFSET_ALL[7:0]
Combined Offset Register Channel 4
0x0
R/W
CHANNEL 4 GAIN UPPER BYTE REGISTER
Address: 0x037, Reset: 0x00, Name: CH4_GAIN_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH4_GAIN_ALL[23:16] (R/W)
Combined gain register Channel 4
Table 98. Bit Descriptions for CH4_GAIN_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH4_GAIN_ALL[23:16]
Combined Gain Register Channel 4
0x0
R/W
CHANNEL 4 GAIN MIDDLE BYTE REGISTER
Address: 0x038, Reset: 0x00, Name: CH4_GAIN_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH4_GAIN_ALL[15:8] (R/W)
Combined gain register Channel 4
Table 99. Bit Descriptions for CH4_GAIN_MID_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0] CH4_GAIN_ALL[15:8]
Combined Gain Register Channel 4
0x0
R/W
CHANNEL 4 GAIN LOWER BYTE REGISTER
Address: 0x039, Reset: 0x00, Name: CH4_GAIN_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH4_GAIN_ALL[7:0] (R/W)
Combined gain register Channel 4
Table 100. Bit Descriptions for CH4_GAIN_LOWER_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH4_GAIN_ALL[7:0]
Combined Gain Register Channel 4
0x0
R/W
Rev. 0 | Page 82 of 98
Data Sheet
AD7771
CHANNEL 5 OFFSET UPPER BYTE REGISTER
Address: 0x03A, Reset: 0x00, Name: CH5_OFFSET_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH5_OFFSET_ALL[23:16] (R/W)
Combined offset register Channel 5
Table 101. Bit Descriptions for CH5_OFFSET_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH5_OFFSET_ALL[23:16]
Combined Offset Register Channel 5
0x0
R/W
CHANNEL 5 OFFSET MIDDLE BYTE REGISTER
Address: 0x03B, Reset: 0x00, Name: CH5_OFFSET_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH5_OFFSET_ALL[15:8] (R/W)
Combined offset register Channel 5
Table 102. Bit Descriptions for CH5_OFFSET_MID_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH5_OFFSET_ALL[15:8]
Combined Offset Register Channel 5
0x0
R/W
CHANNEL 5 OFFSET LOWER BYTE REGISTER
Address: 0x03C, Reset: 0x00, Name: CH5_OFFSET_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH5_OFFSET_ALL[7:0] (R/W)
Combined offset register Channel 5
Table 103. Bit Descriptions for CH5_OFFSET_LOWER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH5_OFFSET_ALL[7:0]
Combined Offset Register Channel 5
0x0
R/W
CHANNEL 5 GAIN UPPER BYTE REGISTER
Address: 0x03D, Reset: 0x00, Name: CH5_GAIN_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH5_GAIN_ALL[23:16] (R/W)
Combined gain register Channel 5
Table 104. Bit Descriptions for CH5_GAIN_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH5_GAIN_ALL[23:16]
Combined Gain Register Channel 5
0x0
R/W
CHANNEL 5 GAIN MIDDLE BYTE REGISTER
Address: 0x03E, Reset: 0x00, Name: CH5_GAIN_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH5_GAIN_ALL[15:8] (R/W)
Combined gain register Channel 5
Table 105. Bit Descriptions for CH5_GAIN_MID_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0] CH5_GAIN_ALL[15:8]
Combined Gain Register Channel 5
0x0
R/W
Rev. 0 | Page 83 of 98
AD7771
Data Sheet
CHANNEL 5 GAIN LOWER BYTE REGISTER
Address: 0x03F, Reset: 0x00, Name: CH5_GAIN_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH5_GAIN_ALL[7:0] (R/W)
Combined gain register Channel 5
Table 106. Bit Descriptions for CH5_GAIN_LOWER_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH5_GAIN_ALL[7:0]
Combined Gain Register Channel 5
0x0
R/W
CHANNEL 6 OFFSET UPPER BYTE REGISTER
Address: 0x040, Reset: 0x00, Name: CH6_OFFSET_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH6_OFFSET_ALL[23:16] (R/W)
Combined offset register Channel 6
Table 107. Bit Descriptions for CH6_OFFSET_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH6_OFFSET_ALL[23:16]
Combined Offset Register Channel 6
0x0
R/W
CHANNEL 6 OFFSET MIDDLE BYTE REGISTER
Address: 0x041, Reset: 0x00, Name: CH6_OFFSET_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH6_OFFSET_ALL[15:8] (R/W)
Combined offset register Channel 6
Table 108. Bit Descriptions for CH6_OFFSET_MID_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH6_OFFSET_ALL[15:8]
Combined Offset Register Channel 6
0x0
R/W
CHANNEL 6 OFFSET LOWER BYTE REGISTER
Address: 0x042, Reset: 0x00, Name: CH6_OFFSET_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH6_OFFSET_ALL[7:0] (R/W)
Combined offset register Channel 6
Table 109. Bit Descriptions for CH6_OFFSET_LOWER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH6_OFFSET_ALL[7:0]
Combined Offset Register Channel 6
0x0
R/W
CHANNEL 6 GAIN UPPER BYTE REGISTER
Address: 0x043, Reset: 0x00, Name: CH6_GAIN_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH6_GAIN_ALL[23:16] (R/W)
Combined gain register Channel 6
Table 110. Bit Descriptions for CH6_GAIN_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH6_GAIN_ALL[23:16]
Combined Gain Register Channel 6
0x0
R/W
Rev. 0 | Page 84 of 98
Data Sheet
AD7771
CHANNEL 6 GAIN MIDDLE BYTE REGISTER
Address: 0x044, Reset: 0x00, Name: CH6_GAIN_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH6_GAIN_ALL[15:8] (R/W)
Combined gain register Channel 6
Table 111. Bit Descriptions for CH6_GAIN_MID_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0] CH6_GAIN_ALL[15:8]
Combined Gain Register Channel 6
0x0
R/W
CHANNEL 6 GAIN LOWER BYTE REGISTER
Address: 0x045, Reset: 0x00, Name: CH6_GAIN_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH6_GAIN_ALL[7:0] (R/W)
Combined gain register Channel 6
Table 112. Bit Descriptions for CH6_GAIN_LOWER_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH6_GAIN_ALL[7:0]
Combined Gain Register Channel 6
0x0
R/W
CHANNEL 7 OFFSET UPPER BYTE REGISTER
Address: 0x046, Reset: 0x00, Name: CH7_OFFSET_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH7_OFFSET_ALL[23:16] (R/W)
Combined offset register Channel 7
Table 113. Bit Descriptions for CH7_OFFSET_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH7_OFFSET_ALL[23:16]
Combined Offset Register Channel 7
0x0
R/W
CHANNEL 7 OFFSET MIDDLE BYTE REGISTER
Address: 0x047, Reset: 0x00, Name: CH7_OFFSET_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH7_OFFSET_ALL[15:8] (R/W)
Combined offset register Channel 7
Table 114. Bit Descriptions for CH7_OFFSET_MID_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH7_OFFSET_ALL[15:8]
Combined Offset Register Channel 7
0x0
R/W
CHANNEL 7 OFFSET LOWER BYTE REGISTER
Address: 0x048, Reset: 0x00, Name: CH7_OFFSET_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH7_OFFSET_ALL[7:0] (R/W)
Combined offset register Channel 7
Table 115. Bit Descriptions for CH7_OFFSET_LOWER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH7_OFFSET_ALL[7:0]
Combined Offset Register Channel 7
0x0
R/W
Rev. 0 | Page 85 of 98
AD7771
Data Sheet
CHANNEL 7 GAIN UPPER BYTE REGISTER
Address: 0x049, Reset: 0x00, Name: CH7_GAIN_UPPER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH7_GAIN_ALL[23:16] (R/W)
Combined gain register Channel 7
Table 116. Bit Descriptions for CH7_GAIN_UPPER_BYTE
Bits
Bit Name
Settings Description
Reset
Access
[7:0] CH7_GAIN_ALL[23:16]
Combined Gain Register Channel 7
0x0
R/W
CHANNEL 7 GAIN MIDDLE BYTE REGISTER
Address: 0x04A, Reset: 0x00, Name: CH7_GAIN_MID_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH7_GAIN_ALL[15:8] (R/W)
Combined gain register Channel 7
Table 117. Bit Descriptions for CH7_GAIN_MID_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0] CH7_GAIN_ALL[15:8]
Combined Gain Register Channel 7
0x0
R/W
CHANNEL 7 GAIN LOWER BYTE REGISTER
Address: 0x04B, Reset: 0x00, Name: CH7_GAIN_LOWER_BYTE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] CH7_GAIN_ALL[7:0] (R/W)
Combined gain register Channel 7
Table 118. Bit Descriptions for CH7_GAIN_LOWER_BYTE
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
CH7_GAIN_ALL[7:0]
Combined Gain Register Channel 7
0x0
R/W
CHANNEL 0 STATUS REGISTER
Address: 0x04C, Reset: 0x00, Name: CH0_ERR_REG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:5] RESERVED
[0] CH0_ERR_REF_DET (R)
Channel 0 - Reference detect error
[4] CH0_ERR_AINM_UV (R)
AIN0- undervoltage error
[1] CH0_ERR_AINP_OV (R)
AIN0+ overvoltage error
[3] CH0_ERR_AINM_OV (R)
AIN0- overvoltage error
[2] CH0_ERR_AINP_UV (R)
AIN0+ undervoltage error
Table 119. Bit Descriptions for CH0_ERR_REG
Bits
Bit Name
Settings
Description
Reset
0x0
0x0
0x0
0x0
0x0
0x0
Access
[7:5] RESERVED
Reserved
R/W
R
R
R
R
4
3
2
1
0
CH0_ERR_AINM_UV
Channel 0—AIN0− Undervoltage Error
Channel 0—AIN0− Overvoltage Error
Channel 0—AIN0+ Undervoltage Error
Channel 0—AIN0+ Overvoltage Error
Channel 0—Reference Detect Error
CH0_ERR_AINM_OV
CH0_ERR_AINP_UV
CH0_ERR_AINP_OV
CH0_ERR_REF_DET
R
Rev. 0 | Page 86 of 98
Data Sheet
AD7771
CHANNEL 1 STATUS REGISTER
Address: 0x04D, Reset: 0x00, Name: CH1_ERR_REG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:5] RESERVED
[0] CH1_ERR_REF_DET (R)
Channel 1 - Reference detect error
[4] CH1_ERR_AINM_UV (R)
AIN1- undervoltage error
[1] CH1_ERR_AINP_OV (R)
AIN1+ overvoltage error
[3] CH1_ERR_AINM_OV (R)
AIN1- overvoltage error
[2] CH1_ERR_AINP_UV (R)
AIN1+ undervoltage error
Table 120. Bit Descriptions for CH1_ERR_REG
Bits
Bit Name
Settings
Description
Reset
0x0
0x0
0x0
0x0
0x0
0x0
Access
[7:5] RESERVED
Reserved
R/W
R
R
R
R
4
3
2
1
0
CH1_ERR_AINM_UV
Channel 1—AIN1− Undervoltage Error
Channel 1—AIN1− Overvoltage Error
Channel 1—AIN1+ Undervoltage Error
Channel 1—AIN1+ Overvoltage Error
Channel 1—Reference Detect Error
CH1_ERR_AINM_OV
CH1_ERR_AINP_UV
CH1_ERR_AINP_OV
CH1_ERR_REF_DET
R
CHANNEL 2 STATUS REGISTER
Address: 0x04E, Reset: 0x00, Name: CH2_ERR_REG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:5] RESERVED
[0] CH2_ERR_REF_DET (R)
Channel 2 - Reference detect error
[4] CH2_ERR_AINM_UV (R)
AIN2- undervoltage error
[1] CH2_ERR_AINP_OV (R)
AIN2+ overvoltage error
[3] CH2_ERR_AINM_OV (R)
AIN2- overvoltage error
[2] CH2_ERR_AINP_UV (R)
AIN2+ undervoltage error
Table 121. Bit Descriptions for CH2_ERR_REG
Bits
Bit Name
Settings
Description
Reset
0x0
0x0
0x0
0x0
0x0
0x0
Access
[7:5] RESERVED
Reserved
R/W
R
R
R
R
4
3
2
1
0
CH2_ERR_AINM_UV
Channel 2—AIN2− Undervoltage Error
Channel 2—AIN2− Overvoltage Error
Channel 2—AIN2+ Undervoltage Error
Channel 2—AIN2+ Overvoltage Error
Channel 2—Reference Detect Error
CH2_ERR_AINM_OV
CH2_ERR_AINP_UV
CH2_ERR_AINP_OV
CH2_ERR_REF_DET
R
Rev. 0 | Page 87 of 98
AD7771
Data Sheet
CHANNEL 3 STATUS REGISTER
Address: 0x04F, Reset: 0x00, Name: CH3_ERR_REG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:5] RESERVED
[0] CH3_ERR_REF_DET (R)
Channel 3 - Reference detect error
[4] CH3_ERR_AINM_UV (R)
AIN3- undervoltage error
[1] CH3_ERR_AINP_OV (R)
AIN3+ overvoltage error
[3] CH3_ERR_AINM_OV (R)
AIN3- overvoltage error
[2] CH3_ERR_AINP_UV (R)
AIN3+ undervoltage error
Table 122. Bit Descriptions for CH3_ERR_REG
Bits
Bit Name
Settings
Description
Reset
0x0
0x0
0x0
0x0
0x0
0x0
Access
[7:5] RESERVED
Reserved
R/W
R
R
R
R
4
3
2
1
0
CH3_ERR_AINM_UV
Channel 3—AIN3− Undervoltage Error
Channel 3—AIN3− Overvoltage Error
Channel 3—AIN3+ Undervoltage Error
Channel 3—AIN3+ Overvoltage Error
Channel 3—Reference Detect Error
CH3_ERR_AINM_OV
CH3_ERR_AINP_UV
CH3_ERR_AINP_OV
CH3_ERR_REF_DET
R
CHANNEL 4 STATUS REGISTER
Address: 0x050, Reset: 0x00, Name: CH4_ERR_REG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:5] RESERVED
[0] CH4_ERR_REF_DET (R)
Channel 4 - Reference detect error
[4] CH4_ERR_AINM_UV (R)
AIN4- undervoltage error
[1] CH4_ERR_AINP_OV (R)
AIN4+ overvoltage error
[3] CH4_ERR_AINM_OV (R)
AIN4- overvoltage error
[2] CH4_ERR_AINP_UV (R)
AIN4+ undervoltage error
Table 123. Bit Descriptions for CH4_ERR_REG
Bits
Bit Name
Settings
Description
Reset
0x0
0x0
0x0
0x0
0x0
0x0
Access
[7:5] RESERVED
Reserved
R/W
R
R
R
R
4
3
2
1
0
CH4_ERR_AINM_UV
Channel 4—AIN4− Undervoltage Error
Channel 4—AIN4− Overvoltage Error
Channel 4—AIN4+ Undervoltage Error
Channel 4—AIN4+ Overvoltage Error
Channel 4—Reference Detect Error
CH4_ERR_AINM_OV
CH4_ERR_AINP_UV
CH4_ERR_AINP_OV
CH4_ERR_REF_DET
R
Rev. 0 | Page 88 of 98
Data Sheet
AD7771
CHANNEL 5 STATUS REGISTER
Address: 0x051, Reset: 0x00, Name: CH5_ERR_REG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:5] RESERVED
[0] CH5_ERR_REF_DET (R)
Channel 5 - Reference detect error
[4] CH5_ERR_AINM_UV (R)
AIN5- undervoltage error
[1] CH5_ERR_AINP_OV (R)
AIN5+ overvoltage error
[3] CH5_ERR_AINM_OV (R)
AIN5- overvoltage error
[2] CH5_ERR_AINP_UV (R)
AIN5+ undervoltage error
Table 124. Bit Descriptions for CH5_ERR_REG
Bits
Bit Name
Settings
Description
Reset
0x0
0x0
0x0
0x0
0x0
0x0
Access
[7:5] RESERVED
Reserved
R/W
R
R
R
R
4
3
2
1
0
CH5_ERR_AINM_UV
Channel 5—AIN5− Undervoltage Error
Channel 5—AIN5− Overvoltage Error
Channel 5—AIN5+ Undervoltage Error
Channel 5—AIN5+ Overvoltage Error
Channel 5—Reference Detect Error
CH5_ERR_AINM_OV
CH5_ERR_AINP_UV
CH5_ERR_AINP_OV
CH5_ERR_REF_DET
R
CHANNEL 6 STATUS REGISTER
Address: 0x052, Reset: 0x00, Name: CH6_ERR_REG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:5] RESERVED
[0] CH6_ERR_REF_DET (R)
Channel 6 - Reference detect error
[4] CH6_ERR_AINM_UV (R)
AIN6- undervoltage error
[1] CH6_ERR_AINP_OV (R)
AIN6+ overvoltage error
[3] CH6_ERR_AINM_OV (R)
AIN6- overvoltage error
[2] CH6_ERR_AINP_UV (R)
AIN6+ undervoltage error
Table 125. Bit Descriptions for CH6_ERR_REG
Bits
Bit Name
Settings
Description
Reset
0x0
0x0
0x0
0x0
0x0
0x0
Access
[7:5] RESERVED
Reserved
R/W
R
R
R
R
4
3
2
1
0
CH6_ERR_AINM_UV
Channel 6—AIN6− Undervoltage Error
Channel 6—AIN6− Overvoltage Error
Channel 6—AIN6+ Undervoltage Error
Channel 6—AIN6+ Overvoltage Error
Channel 6—Reference Detect Error
CH6_ERR_AINM_OV
CH6_ERR_AINP_UV
CH6_ERR_AINP_OV
CH6_ERR_REF_DET
R
Rev. 0 | Page 89 of 98
AD7771
Data Sheet
CHANNEL 7 STATUS REGISTER
Address: 0x053, Reset: 0x00, Name: CH7_ERR_REG
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:5] RESERVED
[0] CH7_ERR_REF_DET (R)
Channel 7 - Reference detect error
[4] CH7_ERR_AINM_UV (R)
AIN7- undervoltage error
[1] CH7_ERR_AINP_OV (R)
AIN7+ overvoltage error
[3] CH7_ERR_AINM_OV (R)
AIN7- overvoltage error
[2] CH7_ERR_AINP_UV (R)
AIN7+ undervoltage error
Table 126. Bit Descriptions for CH7_ERR_REG
Bits
[7:5]
4
3
2
Bit Name
Settings
Description
Reset
0x0
0x0
0x0
0x0
0x0
0x0
Access
RESERVED
Reserved
R
R
R
R
R
R
CH7_ERR_AINM_UV
CH7_ERR_AINM_OV
CH7_ERR_AINP_UV
CH7_ERR_AINP_OV
CH7_ERR_REF_DET
Channel 7—AIN7− Undervoltage Error
Channel 7—AIN7− Overvoltage Error
Channel 7—AIN7+ Undervoltage Error
Channel 7—AIN7+ Overvoltage Error
Channel 7—Reference Detect Error
1
0
CHANNEL 0/CHANNEL 1 DSP ERRORS REGISTER
Address: 0x054, Reset: 0x00, Name: CH0_1_SAT_ERR
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] RESERVED
[0] CH0_ERR_OUTPUT_SAT (R)
Channel 0 - ADC conversion has
exceeded limits and has been clamped
[5] CH1_ERR_MOD_SAT (R)
Channel 1 - Modulator output saturation
error
[1] CH0_ERR_FILTER_SAT (R)
Channel 0 - Filter result has exceeded
a reasonable level, before offset and
gain calibration has been applied.
[4] CH1_ERR_FILTER_SAT (R)
Channel 1 - Filter result has exceeded
a reasonable level, before offset and
gain calibration has been applied.
[2] CH0_ERR_MOD_SAT (R)
Channel 0 - Modulator output saturation
error
[3] CH1_ERR_OUTPUT_SAT (R)
Channel 1 - ADC conversion has
exceeded limits and has been clamped
Table 127. Bit Descriptions for CH0_1_SAT_ERR
Bits Bit Name
Settings Description
Reset Access
[7:6] RESERVED
Reserved
0x0
0x0
R
R
R
5
4
CH1_ERR_MOD_SAT
CH1_ERR_FILTER_SAT
Channel 1—Modulator output saturation error
Channel 1—Filter result has exceeded a reasonable level, before offset and 0x0
gain calibration are applied
3
2
1
CH1_ERR_OUTPUT_SAT
CH0_ERR_MOD_SAT
CH0_ERR_FILTER_SAT
Channel 1—ADC conversion has exceeded limits and is clamped
Channel 0—Modulator output saturation error
Channel 0—Filter result has exceeded a reasonable level, before offset and 0x0
gain calibration are applied
0x0
0x0
R
R
R
0
CH0_ERR_OUTPUT_SAT
Channel 0—ADC conversion has exceeded limits and is clamped
0x0
R
Rev. 0 | Page 90 of 98
Data Sheet
AD7771
CHANNEL 2/CHANNEL 3 DSP ERRORS REGISTER
Address: 0x055, Reset: 0x00, Name: CH2_3_SAT_ERR
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] RESERVED
[0] CH2_ERR_OUTPUT_SAT (R)
Channel 2 - ADC conversion has
exceeded limits and has been clamped
[5] CH3_ERR_MOD_SAT (R)
Channel 3 - Modulator output saturation
error
[1] CH2_ERR_FILTER_SAT (R)
Channel 2 - Filter result has exceeded
a reasonable level, before offset and
gain calibration has been applied.
[4] CH3_ERR_FILTER_SAT (R)
Channel 3 - Filter result has exceeded
a reasonable level, before offset and
gain calibration has been applied.
[2] CH2_ERR_MOD_SAT (R)
Channel 2 - Modulator output saturation
error
[3] CH3_ERR_OUTPUT_SAT (R)
Channel 3 - ADC conversion has
exceeded limits and has been clamped
Table 128. Bit Descriptions for CH2_3_SAT_ERR
Bits Bit Name
Settings Description
Reset Access
[7:6] RESERVED
Reserved
0x0
0x0
R
R
R
5
4
CH3_ERR_MOD_SAT
CH3_ERR_FILTER_SAT
Channel 3—Modulator output saturation error
Channel 3—Filter result has exceeded a reasonable level, before offset and 0x0
gain calibration are applied
3
2
1
CH3_ERR_OUTPUT_SAT
CH2_ERR_MOD_SAT
CH2_ERR_FILTER_SAT
Channel 3—ADC conversion has exceeded limits and is clamped
Channel 2—Modulator output saturation error
Channel 2—Filter result has exceeded a reasonable level, before offset and 0x0
gain calibration are applied
0x0
0x0
R
R
R
0
CH2_ERR_OUTPUT_SAT
Channel 2—ADC conversion has exceeded limits and has been clamped
0x0
R
CHANNEL 4/CHANNEL 5 DSP ERRORS REGISTER
Address: 0x056, Reset: 0x00, Name: CH4_5_SAT_ERR
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] RESERVED
[0] CH4_ERR_OUTPUT_SAT (R)
Channel 4 - ADC conversion has
exceeded limits and has been clamped
[5] CH5_ERR_MOD_SAT (R)
Channel 5 - Modulator output saturation
error
[1] CH4_ERR_FILTER_SAT (R)
Channel 4 - Filter result has exceeded
a reasonable level, before offset and
gain calibration has been applied.
[4] CH5_ERR_FILTER_SAT (R)
Channel 5 - Filter result has exceeded
a reasonable level, before offset and
gain calibration has been applied.
[2] CH4_ERR_MOD_SAT (R)
Channel 4 - Modulator output saturation
error
[3] CH5_ERR_OUTPUT_SAT (R)
Channel 5 - ADC conversion has
exceeded limits and has been clamped
Table 129. Bit Descriptions for CH4_5_SAT_ERR
Bits Bit Name
Settings Description
Reset Access
[7:6] RESERVED
Reserved
0x0
0x0
R
R
R
5
4
CH5_ERR_MOD_SAT
CH5_ERR_FILTER_SAT
Channel 5—Modulator output saturation error
Channel 5—Filter result has exceeded a reasonable level, before offset and 0x0
gain calibration are applied
3
2
1
CH5_ERR_OUTPUT_SAT
CH4_ERR_MOD_SAT
CH4_ERR_FILTER_SAT
Channel 5—ADC conversion has exceeded limits and is clamped
Channel 4—Modulator output saturation error
Channel 4—Filter result has exceeded a reasonable level, before offset and 0x0
gain calibration are applied
0x0
0x0
R
R
R
0
CH4_ERR_OUTPUT_SAT
Channel 4—ADC conversion has exceeded limits and is clamped
0x0
R
Rev. 0 | Page 91 of 98
AD7771
Data Sheet
CHANNEL 6/CHANNEL 7 DSP ERRORS REGISTER
Address: 0x057, Reset: 0x00, Name: CH6_7_SAT_ERR
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] RESERVED
[0] CH6_ERR_OUTPUT_SAT (R)
Channel 6 - ADC conversion has
exceeded limits and has been clamped
[5] CH7_ERR_MOD_SAT (R)
Channel 7 - Modulator output saturation
error
[1] CH6_ERR_FILTER_SAT (R)
Channel 6 - Filter result has exceeded
a reasonable level, before offset and
gain calibration has been applied.
[4] CH7_ERR_FILTER_SAT (R)
Channel 7 - Filter result has exceeded
a reasonable level, before offset and
gain calibration has been applied.
[2] CH6_ERR_MOD_SAT (R)
Channel 6 - Modulator output saturation
error
[3] CH7_ERR_OUTPUT_SAT (R)
Channel 7 - ADC conversion has
exceeded limits and has been clamped
Table 130. Bit descriptions for CH6_7_SAT_ERR
Bits Bit Name
Settings Description
Reset Access
[7:6] RESERVED
Reserved
0x0
0x0
R
R
R
5
4
CH7_ERR_MOD_SAT
CH7_ERR_FILTER_SAT
Channel 7—Modulator output saturation error
Channel 7—Filter result has exceeded a reasonable level, before offset and 0x0
gain calibration are applied
3
2
1
CH7_ERR_OUTPUT_SAT
CH6_ERR_MOD_SAT
CH6_ERR_FILTER_SAT
Channel 7—ADC conversion has exceeded limits and is clamped
Channel 6—Modulator output saturation error
Channel 6—Filter result has exceeded a reasonable level, before offset and 0x0
gain calibration are applied
0x0
0x0
R
R
R
0
CH6_ERR_OUTPUT_SAT
Channel 6—ADC conversion has exceeded limits and is clamped
0x0
R
CHANNEL 0 TO CHANNEL 7 ERROR REGISTER ENABLE REGISTER
Address: 0x058, Reset: 0xFE, Name: CHX_ERR_REG_EN
7
6
5
4
3
2
1
0
1
1
1
1
1
1
1
0
[7] OUTPUT_SAT_TEST_EN (R/W)
[0] REF_DET_TEST_EN (R/W)
ADC conversion error test enable
Reference detect test enable
[6] FILTER_SAT_TEST_EN (R/W)
[1] AINP_OV_TEST_EN (R/W)
Filter saturation error test enable
AINx+ overvoltage test enable
[5] MOD_SAT_TEST_EN (R/W)
[2] AINP_UV_TEST_EN (R/W)
Enable error flag for Modulator saturation
AINx+ undervoltage test enable
[4] AINM_UV_TEST_EN (R/W)
[3] AINM_OV_TEST_EN (R/W)
AINx- undervoltage test enable
AINx- overvoltage test enable
Table 131. Bit Descriptions for CHX_ERR_REG_EN
Bits
Bit Name
Settings Description
Reset
0x1
0x1
0x1
0x1
0x1
0x1
0x1
0x0
Access
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
7
6
5
4
3
2
1
0
OUTPUT_SAT_TEST_EN
FILTER_SAT_TEST_EN
MOD_SAT_TEST_EN
AINM_UV_TEST_EN
AINM_OV_TEST_EN
AINP_UV_TEST_EN
AINP_OV_TEST_EN
REF_DET_TEST_EN
ADC Conversion Error Test Enable
Filter Saturation Test Enable
Enable Error Flag for Modulator Saturation
AINx− Undervoltage Test Enable
AINx− Overvoltage Test Enable
AINx+ Undervoltage Test Enable
AINx+ Overvoltage Test Enable
Reference Detect Test Enable
Rev. 0 | Page 92 of 98
Data Sheet
AD7771
GENERAL ERRORS REGISTER 1
Address: 0x059, Reset: 0x00, Name: GEN_ERR_REG_1
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] RESERVED
[0] SPI_CRC_ERR (R)
SPI CRC error
[5] MEMMAP_CRC_ERR (R)
A CRC of the memory map contents
is run periodically to check for errors
[1] SPI_INVALID_WRITE_ERR (R)
SPI invalid write address
[4] ROM_CRC_ERR (R)
A CRC of the fuse contents is run
periodically to check for errors in
the fuses
[2] SPI_INVALID_READ_ERR (R)
SPI invalid read address
[3] SPI_CLK_COUNT_ERR (R)
SPI clock counter error
Table 132. Bit Descriptions for GEN_ERR_REG_1
Bits Bit Name
Settings Description
Reset Access
[7:6] RESERVED
Reserved
0x0
R
R
R
R
R
R
R
5
4
3
2
1
0
MEMMAP_CRC_ERR
ROM_CRC_ERR
SPI_CLK_COUNT_ERR
SPI_INVALID_READ_ERR
SPI_INVALID_WRITE_ERR
SPI_CRC_ERR
A CRC of the memory map contents is run periodically to check for errors 0x0
A CRC of the fuse contents is run periodically to check for errors in the fuses
SPI clock counter error
SPI invalid read address
SPI invalid write address
SPI CRC error
0x0
0x0
0x0
0x0
0x0
GENERAL ERRORS REGISTER 1 ENABLE
Address: 0x05A, Reset: 0x3E, Name: GEN_ERR_REG_1_EN
Table 133. Bit Descriptions for GEN_ERR_REG_1_EN
Bits Bit Name
Settings Description
Reset
0x0
0x1
0x1
0x1
0x1
0x1
0x0
Access
R
[7:6] RESERVED
Reserved
Memory Map CRC Test Error Enable
Fuse CRC Test Enable
SPI Clock Counter Test Enable
SPI Invalid Read Address Test Enable
SPI Invalid Write Address Test Enable
SPI CRC Error Test Enable
5
4
3
2
1
0
MEMMAP_CRC_TEST_EN
ROM_CRC_TEST_EN
SPI_CLK_COUNT_TEST_EN
SPI_INVALID_READ_TEST_EN
SPI_INVALID_WRITE_TEST_EN
SPI_CRC_TEST_EN
R/W
R/W
R/W
R/W
R/W
R/W
Rev. 0 | Page 93 of 98
AD7771
Data Sheet
GENERAL ERRORS REGISTER 2
Address: 0x05B, Reset: 0x00, Name: GEN_ERR_REG_2
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] RESERVED
[0] DLDO_PSM_ERR (R)
DRegCap power supply error
[5] RESET_DETECTED (R)
Reset detected
[1] ALDO2_PSM_ERR (R)
AReg2Cap power supply error
[4] EXT_MCLK_SWITCH_ERR (R)
Clock not switched over
[2] ALDO1_PSM_ERR (R)
AReg1Cap power supply error
[3] RESERVED
Table 134. Bit Descriptions for GEN_ERR_REG_2
Bits
Bit Name
Settings Description
Reset
0x0
0x0
0x0
0x0
0x0
0x0
0x0
Access
[7:6] RESERVED
Reserved
Reset Detected
R
R
R
R
R
R
R
5
4
3
2
1
0
RESET_DETECTED
EXT_MCLK_SWITCH_ERR
RESERVED
ALDO1_PSM_ERR
ALDO2_PSM_ERR
DLDO_PSM_ERR
Clock Not Switched Over
Reserved
AREG1CAP Power Supply Error
AREG2CAP Power Supply Error
DREGCAP Power Supply Error
GENERAL ERRORS REGISTER 2 ENABLE
Address: 0x05C, Reset: 0x3C, Name: GEN_ERR_REG_2_EN
7
6
5
4
3
2
1
0
0
0
1
0
1
1
0
0
[7:6] RESERVED
[1:0] LDO_PSM_TRIP_TEST_EN (R/W)
LDO PSM trip test enable
0: 00 - No trip detect test enabled.
1: 01 - Run trip detect test on AReg1Cap.
10: 10 - Run trip detect test on AReg2Cap.
11: 11 - Run trip detect test on DRegCap.
[5] RESET_DETECT_EN (R/W)
Reset detect enable
[4] RESERVED
[3:2] LDO_PSM_test_EN (R/W)
LDO PSM test EN
0: 00 - No power supply monitor test
enabled.
1: 01 - Run power supply monitor test
on ARegxCap.
10: 10 - Run power supply monitor test
on DRegCap.
11: 11 - Run power supply monitor test
on all LDOs.
Table 135. Bit Descriptions for GEN_ERR_REG_2_EN
Bits Bit Name
Settings Description
Reset
0x0
Access
R
[7:6] RESERVED
Reserved
5
4
RESET_DETECT_EN
RESERVED
Reset Detect Enable
Reserved
0x1
R/W
R/W
R/W
0x1
[3:2] LDO_PSM_TEST_EN
LDO PSM Test Enable
0x3
0
1
00—No power supply monitor test enabled
01—Run power supply monitor test on AREGxCAP
10 10—Run power supply monitor test on DREGCAP
11 11—Run power supply monitor test on all LDOs
LDO PSM Trip Test Enable
[1:0] LDO_PSM_TRIP_TEST_EN
0x0
R/W
0
1
00—No trip detect test enabled
01—Run trip detect test on AREG1CAP
10 10—Run trip detect test on AREG2CAP
11 11—Run trip detect test on DREGCAP
Rev. 0 | Page 94 of 98
Data Sheet
AD7771
ERROR STATUS REGISTER 1
Address: 0x05D, Reset: 0x00, Name: STATUS_REG_1
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] RESERVED
[0] ERR_LOC_CH0 (R)
An error specific to CH0_ERR_REG
is active
[5] CHIP_ERROR (R)
Set high if any error bit is high
[1] ERR_LOC_CH1 (R)
An error specific to CH1_ERR_REG
is active
[4] ERR_LOC_CH4 (R)
An error specific to CH4_ERR_REG
is active
[2] ERR_LOC_CH2 (R)
An error specific to CH2_ERR_REG
is active
[3] ERR_LOC_CH3 (R)
An error specific to CH3_ERR_REG
is active
Table 136. Bit Descriptions for STATUS_REG_1
Bits Bit Name Settings Description
[7:6] RESERVED Reserved
Set this bit high if any error bit is high
Reset
0x0
0x0
0x0
0x0
0x0
0x0
0x0
Access
R
R
R
R
R
R
R
5
4
3
2
1
0
CHIP_ERROR
ERR_LOC_CH4
ERR_LOC_CH3
ERR_LOC_CH2
ERR_LOC_CH1
ERR_LOC_CH0
An error specific to CH4_ERR_REG is active
An error specific to CH3_ERR_REG is active
An error specific to CH2_ERR_REG is active
An error specific to CH1_ERR_REG is active
An error specific to CH0_ERR_REG is active
ERROR STATUS REGISTER 2
Address: 0x05E, Reset: 0x00, Name: STATUS_REG_2
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] RESERVED
[0] ERR_LOC_CH5 (R)
An error specific to CH5_ERR_REG
is active
[5] CHIP_ERROR (R)
Set high if any error bit is high
[1] ERR_LOC_CH6 (R)
An error specific to CH6_ERR_REG
is active
[4] ERR_LOC_GEN2 (R)
An error specific to GEN_ERR_REG_2
is active
[2] ERR_LOC_CH7 (R)
An error specific to CH7_ERR_REG
is active
[3] ERR_LOC_GEN1 (R)
An error specific to GEN_ERR_REG_1
is active
Table 137. Bit Descriptions for STATUS_REG_2
Bits
[7:6]
5
4
3
2
1
0
Bit Name
Settings
Description
Reset
0x0
0x0
0x0
0x0
0x0
0x0
0x0
Access
RESERVED
Reserved
Set high if any error bit is high
R
R
R
R
R
R
R
CHIP_ERROR
ERR_LOC_GEN2
ERR_LOC_GEN1
ERR_LOC_CH7
ERR_LOC_CH6
ERR_LOC_CH5
An error specific to GEN_ERR_REG_2 is active
An error specific to GEN_ERR_REG_1 is active
An error specific to CH7_ERR_REG is active
An error specific to CH6_ERR_REG is active
An error specific to CH5_ERR_REG is active
Rev. 0 | Page 95 of 98
AD7771
Data Sheet
ERROR STATUS REGISTER 3
Address: 0x05F, Reset: 0x00, Name: STATUS_REG_3
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:6] RESERVED
[0] ERR_LOC_SAT_CH0_1 (R)
An error specific to CH0_1_SAT_ERR
reg is active
[5] CHIP_ERROR (R)
Set high if any error bit is high
[1] ERR_LOC_SAT_CH2_3 (R)
An error specific to CH2_3_SAT_ERR
reg is active
[4] INIT_COMPLETE (R)
Fuse initialization is complete. Device
is ready to receive commands
[2] ERR_LOC_SAT_CH4_5 (R)
An error specific to CH4_5_SAT_ERR
reg is active
[3] ERR_LOC_SAT_CH6_7 (R)
An error specific to CH6_7_SAT_ERR
reg is active
Table 138. Bit Descriptions for STATUS_REG_3
Bits Bit Name
Settings Description
Reset Access
[7:6] RESERVED
Reserved
Set high if any error bit is high.
0x0
0x0
0x0
0x0
0x0
0x0
0x0
R
R
R
R
R
R
R
5
4
3
2
1
0
CHIP_ERROR
INIT_COMPLETE
ERR_LOC_SAT_CH6_7
ERR_LOC_SAT_CH4_5
ERR_LOC_SAT_CH2_3
ERR_LOC_SAT_CH0_1
Fuse initialization is complete. Device is ready to receive commands.
An error specific to CH6_7_SAT_ERR register is active.
An error specific to CH4_5_SAT_ERR register is active.
An error specific to CH2_3_SAT_ERR register is active.
An error specific to CH0_1_SAT_ERR register is active.
DECIMATION RATE (N) MSB REGISTER
Address: 0x060, Reset: 0x00, Name: SRC_N_MSB
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:4] RESERVED
[3:0] SRC_N_ALL[11:8] (R/W)
SRC N Combined
Table 139. Bit Descriptions for SRC_N_MSB
Bits
[7:4]
[3:0]
Bit Name
Settings
Description
Reset
0x0
0x0
Access
R
R/W
RESERVED
SRC_N_ALL[11:8]
Reserved
SRC N Combined
DECIMATION RATE (N) LSB REGISTER
Address: 0x061, Reset: 0x80, Name: SRC_N_LSB
7
6
5
4
3
2
1
0
1
0
0
0
0
0
0
0
[7:0] SRC_N_ALL[7:0] (R/W)
SRC N Combined
Table 140. Bit Descriptions for SRC_N_LSB
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
SRC_N_ALL[7:0]
SRC N Combined
0x0
R/W
DECIMATION RATE (IF) MSB REGISTER
Address: 0x062, Reset: 0x00, Name: SRC_IF_MSB
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] SRC_IF_ALL[15:8] (R/W)
SRC IF ALL
Table 141. Bit Descriptions for SRC_IF_MSB
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
SRC_IF_ALL[15:8]
SRC IF All
0x0
R/W
Rev. 0 | Page 96 of 98
Data Sheet
AD7771
DECIMATION RATE (IF) LSB REGISTER
Address: 0x063, Reset: 0x00, Name: SRC_IF_LSB
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7:0] SRC_IF_ALL[7:0] (R/W)
SRC IF ALL
Table 142. Bit Descriptions for SRC_IF_LSB
Bits
Bit Name
Settings
Description
Reset
Access
[7:0]
SRC_IF_ALL[7:0]
SRC IF All
0x0
R/W
SRC LOAD SOURCE AND LOAD UPDATE REGISTER
Address: 0x064, Reset: 0x00, Name: SRC_UPDATE
7
6
5
4
3
2
1
0
0
0
0
0
0
0
0
0
[7] SRC_LOAD_SOURCE (R/W)
Select which option to load an SRC
update
[0] SRC_LOAD_UPDATE (R/W)
Assert bit to load SRC registers into
SRC
[6:1] RESERVED
Table 143. Bit Descriptions for SRC_UPDATE
Bits
Bit Name
Settings
Description
Reset
0x0
0x0
Access
R/W
R
7
SRC_LOAD_SOURCE
Selects which option to load an SRC update
Reserved
Asserts bit to load SRC registers into SRC
[6:1] RESERVED
SRC_LOAD_UPDATE
0
0x0
R/W
Rev. 0 | Page 97 of 98
AD7771
Data Sheet
OUTLINE DIMENSIONS
9.10
9.00 SQ
8.90
0.30
0.25
0.18
PIN 1
INDICATOR
PIN 1
INDICATOR
49
64
1
48
0.50
BSC
EXPOSED
PAD
7.70
7.60 SQ
7.50
33
16
32
17
0.45
0.40
0.35
0.20 MIN
TOP VIEW
BOTTOM VIEW
7.50 REF
0.80
0.75
0.70
0.05 MAX
0.02 NOM
COPLANARITY
0.08
0.203 REF
SEATING
PLANE
COMPLIANT TO JEDEC STANDARDS MO-220-WMMD
Figure 139. 64-Lead Lead Frame Chip Scale Package [LFCSP]
9 mm × 9 mm Body and 0.75 mm Package Height
(CP-64-15)
Dimensions shown in millimeters
ORDERING GUIDE
Model1
Temperature Range
Package Description
Package Option
CP-64-15
CP-64-15
AD7771BCPZ
AD7771BCPZ-RL
EVAL-AD7771FMCZ
−40°C to +125°C
−40°C to +125°C
64-Lead Lead Frame Chip Scale Package [LFCSP]
64-Lead Lead Frame Chip Scale Package [LFCSP]
Evaluation Board
1 Z = RoHS Compliant Part.
©2017 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D13802-0-6/17(0)
Rev. 0 | Page 98 of 98
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