ADS7870EAG4 [TI]
12-BIT, 52-kSPS, DATA ACQUISITION SYSTEM WITH ANALOG-TO-DIGITAL CONVERTER, MUX, PGA, AND REFERENCE; 12位， 52 kSPS时，随着模拟数字转换器， MUX ， PGA和引用数据采集系统
| 型号： | ADS7870EAG4 |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | 12-BIT, 52-kSPS, DATA ACQUISITION SYSTEM WITH ANALOG-TO-DIGITAL CONVERTER, MUX, PGA, AND REFERENCE |
| 文件： | 总43页 (文件大小：494K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
ꢀ
ꢁ
ꢂ
ꢃ
ꢄ
ꢃ
ꢅ
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
ꢆ
ꢇ
ꢈ
ꢉ
ꢊ
ꢋ
ꢌ
ꢍ
ꢇ
ꢈ
ꢎ
ꢂ
ꢏ
ꢂ
ꢌ
ꢁ
ꢀ
ꢋ
ꢀ
ꢀ
ꢐ
ꢑ
ꢒ
ꢊ
ꢂ
ꢊ
ꢋ
ꢊ
ꢓ
ꢔ
ꢂ
ꢕ
ꢂ
ꢋ
ꢖ
ꢗ
ꢘ
ꢊ
ꢋ
ꢙ
ꢀ
ꢔ
ꢀ
ꢚ
ꢓ
ꢛ
ꢈ
ꢋ
ꢓ
ꢈ
ꢁ
ꢊ
ꢛ
ꢊ
ꢋ
ꢀ
ꢚ
ꢐ
ꢓ
ꢔ
ꢜ
ꢖ
ꢝ
ꢋ
ꢖ
ꢝ
ꢌ
ꢗ
ꢒ
ꢞ
ꢌ
ꢏ
ꢛ
ꢀ
ꢌ
ꢀ
ꢔ
ꢁ
ꢝ
ꢖ
ꢟ
ꢖ
ꢝ
ꢖ
ꢔ
ꢐ
ꢖ
FEATURES
DESCRIPTION
D
D
PGA Gains: 1, 2, 4, 5, 8, 10, 16, 20 V/V
Programmable Input (Up to 4-Channel
Differential/Up to 8-Channel Single-Ended or
Some Combination)
The ADS7870 (US patents 6140872, 6060874) is a
complete low-power data acquisition system on a single
chip. It consists of a 4-channel differential/8-channel
single-ended multiplexer, precision programmable gain
amplifier, 12-bit successive approximation analog-to-
digital (A/D) converter, and a precision voltage reference.
D
D
1.15-V, 2.048-V, or 2.5-V Internal Reference
SPI/DSP Compatible Serial Interface
(≤ 20 MHz)
Throughput Rate: 52 kSamples/sec
The programmable-gain amplifier provides high input
impedance, excellent gain accuracy, good common-mode
rejection, and low noise.
D
D
D
D
D
D
D
Error Overload Indicator
For many low-level signals, no external amplification or
impedance buffering is needed between the signal source
and the A/D input.
Programmable Output 2s Complement/Binary
2.7-V to 5.5-V Single Supply Operation
4-Bit Digital I/O Via Serial Interface
Pin-Compatible With ADS7871
SSOP-28 Package
The offset voltage of the PGA is auto-zeroed. Gains of 1,
2, 4, 5, 8, 10, 16, and 20 V/V allow signals as low as 125
mV to produce full-scale digital outputs.
The ADS7870 contains an internal reference, which is
trimmed for high initial accuracy and stability vs
temperature. Drift is typically 10 ppm/°C. An external
reference can be used in situations where multiple
ADS7870s share a common reference.
APPLICATIONS
D
D
D
D
Portable Battery-Powered Systems
Low-Power Instrumentation
Low-Power Control Systems
Smart Sensor Applications
The serial interface allows the use of SPI, QSPI,
Microwire, and 8051-family protocols, without glue logic.
BUFIN
BUFOUT/REFIN
REF
VREF
CCLK
Oscillator
LN0
LN1
LN2
LN3
LN4
LN5
LN6
LN7
OSC ENABLE
+
BUSY
12-BIT
A/D
PGA
MUX
_
CONVERT
RESET
RISE/FALL
CS
Serial
Interface
SCLK
I/O0
I/O1
I/O2
I/O3
Digital
I/O
DIN
Registers
DOUT
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments
semiconductor products and disclaimers thereto appears at the end of this data sheet.
QSPI and SPI are trademarks of Motorola, Inc.
Microwire is a trademark of National Semiconductor Corporation.
All other trademarks are the property of their respective owners.
ꢏꢝ ꢓ ꢁꢒ ꢐ ꢋꢊ ꢓꢔ ꢁ ꢀꢋꢀ ꢠꢡ ꢢꢣ ꢤ ꢥꢦ ꢧꢠꢣꢡ ꢠꢨ ꢩꢪ ꢤ ꢤ ꢫꢡꢧ ꢦꢨ ꢣꢢ ꢬꢪꢭ ꢮꢠꢩ ꢦꢧꢠ ꢣꢡ ꢯꢦ ꢧꢫꢰ ꢏꢤ ꢣꢯꢪ ꢩꢧꢨ
ꢩ ꢣꢡ ꢢꢣꢤ ꢥ ꢧꢣ ꢨ ꢬꢫ ꢩ ꢠ ꢢꢠ ꢩ ꢦ ꢧꢠ ꢣꢡꢨ ꢬ ꢫꢤ ꢧꢱꢫ ꢧꢫ ꢤ ꢥꢨ ꢣꢢ ꢋꢫꢲ ꢦꢨ ꢊꢡꢨ ꢧꢤ ꢪꢥ ꢫꢡꢧ ꢨ ꢨꢧ ꢦꢡꢯ ꢦꢤ ꢯ ꢳ ꢦꢤ ꢤ ꢦ ꢡꢧꢴꢰ
ꢏꢤ ꢣ ꢯꢪꢩ ꢧ ꢠꢣ ꢡ ꢬꢤ ꢣ ꢩ ꢫ ꢨ ꢨ ꢠꢡ ꢵ ꢯꢣ ꢫ ꢨ ꢡꢣꢧ ꢡꢫ ꢩꢫ ꢨꢨ ꢦꢤ ꢠꢮ ꢴ ꢠꢡꢩ ꢮꢪꢯ ꢫ ꢧꢫ ꢨꢧꢠ ꢡꢵ ꢣꢢ ꢦꢮ ꢮ ꢬꢦ ꢤ ꢦꢥ ꢫꢧꢫ ꢤ ꢨꢰ
Copyright 1999−2005, Texas Instruments Incorporated
ꢀ
ꢁ
ꢂ
ꢃ
ꢄ
ꢃ
ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
(1)
ORDERING INFORMATION
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
DESIGNATOR
PACKAGE
MARKING
ORDERING
NUMBER
TRANSPORT MEDIA,
QUANTITY
PRODUCT
PACKAGE-LEAD
ADS7870
ADS7870
ADS7870IDB
Rails, 48
ADS7870
SSOP-28 Surface Mount
DB
−40°C to +85°C
ADS7870IDBR
Tape and Reel, 1000
(1)
For the most current package and ordering information, see the Package Option Addendum at the end of this data sheet, or see the TI web
site at www.ti.com.
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate
precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to
damage because very small parametric changes could cause the device not to meet its published specifications.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range unless otherwise noted
(1)
UNIT
5.5 V
Supply voltage, V
Analog inputs
DD
Momentary
Continuous
100 mA
Input current
10 mA
Input voltage
Operating free-air temperature range, T
V
DD
+ 0.5 V to GND − 0.5 V
−40°C to 85°C
−65°C to 150°C
150°C
A
Storage temperature range, T
STG
Junction temperature (T max)
J
Lead temperature, soldering (10 sec)
300°C
(1)
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and
functionaloperation of the device at these or any other conditions beyond those indicated under recommended operating conditions is not implied.
Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
2
ꢀ
ꢁ
ꢂ
ꢃ
ꢄ
ꢃ
ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
ELECTRICAL CHARACTERISTICS
(1)
For the Total System , −40°C ≤ T ≤ 85°C, V
otherwise noted).
= 5 V, BUFIN = 2.5 V (using external reference), 2.5-MHz CCLK and 2.5-MHz SCLK (unless
A
DD
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Analog Input
Input voltage (LNx inputs)
Linear operation
−0.2
V
DD
+ 0.2
V
(2)
Input capacitance
4 to 9.7
6
pF
Common mode
Differential
(2)
Input impedance
MΩ
7
(3)
Channel-to-channel crosstalk
Maximum leakage current
Static Accuracy
Resolution
V = 2 V , 60 Hz
PP
100
100
dB
pA
I
12
Bits
Bits
No missing codes
Integral linearity
G = 1 to 20 V/V
G = 1 to 20 V/V
G = 1 to 20 V/V
G = 1 to 20 V/V
G = 1 to 10 V/V
G = 16 and 20 V/V
G = 1 to 10 V/V
G = 16 and 20 V/V
12
−2.5
2
0.5
1
2.5
LSB
Differential linearity
Offset error
LSB
−6
−0.2
6
0.2
LSB
%FSR
%FSR
%FSR
%FSR
Ratiometric configuration or
(4)
external reference
−0.25
−0.35
−0.4
0.25
0.35
0.4
Full-scale gain error
Internal reference
V = −0.2 V to 5.2 V,
I
DC common-mode rejection ratio, RTI
92
dB
dB
G = 20 V/V
Power supply rejection ratio, RTI
V
DD
= 5 V 10%, G = 20 V/V
86
Dynamic Characteristics
Continuous mode
Address mode
One channel
52
52
20
Throughput rate
ksample/s
Different channels
(5)
External clock, CCLK
0.1
MHz
MHz
MHz
ns
Internal oscillator frequency
Serial interface clock, SCLK
Data setup time
2.5
20
10
10
Data hold time
ns
Digital Inputs
Low-level input voltage, V
IL
0.8
V
V
V
V
V
≤ 3.6 V
2
3
DD
High-level input voltage, V
IH
> 3.6 V
Logic levels
DD
Low-level input current, I
IL
1
1
µA
High-level input current, I
IH
(1)
(2)
The specifications for the total system are overall analog input to digital output specifications. The specifications for internal functions indicate
the performance of the individual functions in the ADS7870.
The ADS7870 uses switched capacitor techniques for the programmable gain amplifier and A/D converter. A characteristic of such circuits is that
the input capacitance at any selected LNx pin changes during the conversion cycle.
(3)
(4)
One channel on with its inputs grounded. All other channels off with sinewave voltage applied to their inputs.
Ratiometricconfiguration exists when the input source is configured such that changes in the reference cause corresponding changes in the input
voltage. The same accuracy applies when a perfect external reference is used.
The CCLK is divided by the DF value specified by the contents of register 3, A/D Control register, bits D0 and D1 to produce DCLK. The maximum
value of DCLK is 2.5 MHz.
(5)
3
ꢀ
ꢁ
ꢂ
ꢃ
ꢄ
ꢃ
ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
ELECTRICAL CHARACTERISTICS
(1)
For the Total System , −40°C ≤ T ≤ 85°C, V
= 5 V, BUFIN = 2.5 V (using external reference), 2.5-MHz CCLK and 2.5-MHz SCLK (unless
A
DD
otherwise noted).
PARAMETER
Digital Outputs
Data coding
TEST CONDITIONS
MIN
TYP
MAX
UNIT
Binary 2s complement
I
I
I
I
= 5 mA
0.4
SINK
Low-level output voltage, V
OL
V
V
= 16 mA
0.8
4.6
5
SINK
Logic levels
= 0.5 mA
= 5 mA
V
DD
− 0.4
SOURCE
SOURCE
High-level output voltage, V
OH
Leakage current
Hi-Z state, V = 0 V to V
O
1
µA
DD
Output capacitance
Voltage Reference
pF
Pin 26 used as output,
Use internal OSC or external
CCLK as conversion clock
V
V
= 2.048 V, 2.5 V
= 1.15 V
−0.25
0.9
0.05
0.25 %FSR
REF
Bandgap voltage
reference
1.15
0.6
V
REF
Output drive
µA
Reference Buffer
Input voltage, BUFIN
Input impedance, BUFIN
Input offset
V
DD
− 0.2
10
V
At pin 27
1000||3
1
GΩ||pF
mV
−10
−0.25
0.05
10
0.25 %FSR
50 ppm/°C
mA
Output voltage accuracy vs temperature,
(2) (3)
Pin 28 used as output,
BUFOUT/REFIN
V
REF
= 2.048 V and 2.5 V
Output drive, BUFOUT/REFIN
Power Supply Requirements
Supply voltage
20
2.7
5.5
V
REF and BUF on, Internal os-
cillator on
1-kHz Sample rate
0.45
1.2
mA
REF and BUF on, External
CCLK
(2)
50-kHz Sample rate
Power down
1.7
1
mA
µA
Power supply current
REF, BUF, Internal
oscillator off
REF and BUF on, Internal
oscillator on
1-kHz Sample rate
2.25
6
mW
(2)
REF and BUF on, External
CCLK
Power dissipation
50-kHz Sample rate
Power down
8.5
5
mW
REF and BUF off
µW
Temperature Range
Operating free-air
Storage range
−40
−65
85
°C
°C
150
Thermal resistance, Q
65
°C/W
JA
(1)
(2)
The specifications for the total system are overall analog input to digital output specifications. The specifications for internal functions indicate
the performance of the individual functions in the ADS7870.
REF and BUF contribute 190 µA and 150 µA (950 µW and 750 µW) respectively. At initial power up the default condition for both REF and BUF
functions is power off. They can be turned on under software control by writing a 1 to D3 and D2 of register 7, REF/OSCILLATOR CONTROL
register.
(3)
For V
< 3 V, V = 2.5 V is not usable.
DD
REF
4
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
ELECTRICAL CHARACTERISTICS
(1)
For Internal Functions , −40°C ≤ T ≤ 85°C, V
= 5 V, BUFIN = 2.5 V (using external reference), 2.5-MHz CCLK and 2.5-MHz SCLK (unless
A
DD
otherwise noted).
PARAMETER
Multiplexer
TEST CONDITIONS
MIN
TYP
MAX
UNIT
On resistance
Off resistance
On channel = 5.2 V,
100
1
Ω
GΩ
V
LNx
= 5.2 V
100
100
100
100
pA
pA
pA
pA
Off channel = 0 V
Off channel leakage
current
On channel = 0 V,
Off channel = 5.2 V
On channel = 5.2 V,
Off channel = 0 V
On channel leakage
current
On channel = 0 V,
Off channel = 5.2 V
PGA Amplifier
(2)
Input capacitance
4 to 9.7
6
pF
MΩ
MΩ
µV
Common mode
Differential
(2)
Input impedance
7
Offset voltage
100
5/Gain
0.3
Small signal bandwidth
MHz
µs
G = 1
G = 20
Settling time
6.4
µs
Analog-To-Digital Converter DC Characteristics
Resolution
12
0.5
0.5
12
Bits
LSB
LSB
Bits
LSB
%
Integral linearity error
Differential linearity error
No missing codes
Offset error
REFIN = 2.5 V
0.5
0.02
80
Full-scale (gain) error
Common mode rejection, RTI of A/D
Power supply rejection, RTI of ADS7870
PGA Plus A/D Converter Sampling Dynamics
Throughput rate
dB
External reference, V
= 5 V 10%
60
dB
DD
f
= 2.5 MHz, DF = 1
CCLK
48 CCLK cycles
12 CCLK cycles
28 CCLK cycles
8 CCLK cycles
36 CCLK cycles
52
4.8
9.6
3.2
12.8
5
kHz
µs
Conversion time
Acquisition time
µs
Auto zero time
µs
Aperture delay
µs
Small signal bandwidth
Step response
MHz
1 Complete Conversion Cycle
(1)
(2)
The specifications for the total system are overall analog input to digital output specifications. The specifications for internal functions indicate
the performance of the individual functions in the ADS7870.
The ADS7870 uses switched capacitor techniques for the programmable gain amplifier and A/D converter. A characteristic of such circuits is that
the input capacitance at any selected LNx pin changes during the conversion cycle.
5
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
PIN ASSIGNMENTS
SSOP-28 PACKAGE
(TOP VIEW)
LN0
LN1
LN2
LN3
LN4
LN5
LN6
LN7
BUFOUT/REFIN
BUFIN
VREF
1
28
27
26
25
24
23
22
21
20
19
18
17
2
3
GND
4
V
5
DD
CS
6
DOUT
DIN
7
8
RESET
RISE/FALL
I/O0
SCLK
9
CCLK
OSC ENABLE
BUSY
10
11
12
I/O1
I/O2 13
14
16 CONVERT
15
I/O3
NC
Terminal Functions
TERMINAL
NAME
NO.
1−8
9
I/O
AI
DESCRIPTION
LN0−LN7
RESET
MUX input lines 0−7
Master reset, zeros all registers
Sets the active edge for SCLK. 0 sets SCLK active on falling edge. 1 sets SCLK active on rising edge.
DI
DI
10
RISE/FALL
11−14 I/O0−I/O3
DIO Digital input or output signal
15
16
17
18
19
NC
−
No connection or internal function. It is recommended that this pin be tied to ground.
0 to 1 transition starts a conversion cycle.
CONVERT
BUSY
DI
DO 1 indicates converter is busy
DI 0 sets CCLK as an input, 1 sets CCLK as an output and turns the oscillator on.
OSC ENABLE
CCLK
DIO If OSC ENABLE = 1, then the internal oscillator is output to this pin. If OSC ENABLE = 0, then this is the input
pin for an external conversion clock.
20
21
22
23
SCLK
DIN
DI
Serial data input/output transfer clock. Active edge set by the RISE/FALL pin. If RISE/FALL is low, SCLK is
active on the falling edge.
DIO Serial data input. In the 3-wire mode, this pin is used for serial data input. In the 2-wire mode, serial data
output appears on this pin as well as the DOUT pin.
DOUT
CS
DO Serial data output. This pin is driven when CS is low and is high impedance when CS is high. This pin
behaves the same in both 3-wire and 2-wire modes.
DI
Chip select. When CS is low, the serial interface is enabled. When CS is high, the serial interface is disabled,
the DOUT pin is high impedance, and the DIN pin is an input. The CS pin only affects the operation of the
serial interface. It does not directly enable/disable the operation of the signal conversion process.
24
25
26
27
28
V
−
−
Power supply voltage, 2.7 V to 5.5 V
Power supply ground
DD
GND
VREF
AO 2.048-/2.5-V on-chip voltage reference
AI Input to reference buffer amplifier
AIO Output from reference buffer amplifier and reference input to ADC
BUFIN
BUFOUT/REFIN
6
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
†
TYPICAL PERFORMANCE CURVES
GAIN ERROR
vs
OUTPUT OFFSET ERROR
vs
FREE-AIR TEMPERATURE
FREE-AIR TEMPERATURE
15
10
5
10
8
Gain = 20
Gain = 8
Gain = 1
6
Gain = 20
Gain = 8
Gain = 1
4
2
0
0
−5
−2
−4
−10
−60 −40 −20
0
20 40 60 80 100 120 140
−60 −40 −20
0
20 40 60 80 100 120 140
T
A
− Free-Air Temperature − °C
T
A
− Free-Air Temperature − °C
Figure 1
Figure 2
VOLTAGE REFERENCE ERROR
vs
INTERNAL OSCILLATOR FREQUENCY
vs
FREE-AIR TEMPERATURE
FREE-AIR TEMPERATURE
0.4
0.2
2.55
2.50
2.45
3 Sigma
Avg
3 Sigma
V
REF
0
−0.2
−0.4
−0.6
2.40
2.35
2.30
−3 Sigma
−3 Sigma
−0.8
−1
2.25
2.20
V
= 2.048 V or 2.5 V
REF
−60 −40 −20
0
20 40 60 80 100 120 140
−60 −40 −20
0
20 40 60 80 100 120 140
T
A
− Free-Air Temperature − °C
T
A
− Free-Air Temperature − °C
Figure 3
Figure 4
†
At T = 25°C, V
DD
= 5 V, V
REF
= 2.5 V connected to BUFIN (using internal reference), 2.5 MHz CCLK, and 2.5 MHz SCLK (unless otherwise noted)
A
7
ꢀ
ꢁ
ꢂ
ꢃ
ꢄ
ꢃ
ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
OUTPUT OFFSET ERROR
vs
COMMON-MODE VOLTAGE
OUTPUT OFFSET ERROR
vs
POWER SUPPLY VOLTAGE
2
8
7
6
5
4
3
2
1
50 Ksps, CCLK = 2.5 MHz,
= 2.048 V
V
1.5
Gain = 20
REF
Gain = 10
1
Gain = 1
Gain = 10
0.5
0
Gain = 1
Gain = 20
−0.5
−1
1 LSB =
4 LSB =
86 dB for Gain = 20,
60 dB for Gain = 1
−72 dB for Gain = 1,
−98 dB for Gain = 20
−1.5
0
−2
−1
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
2
2.5
3
3.5
4
4.5
5
5.5
6
Common-Mode Voltage − V
V
DD
− Supply Voltage − V
Figure 5
Figure 6
QUIESCENT CURRENT
vs
PEAK-TO-PEAK OUTPUT NOISE
vs
GAIN
SAMPLING RATE
1.4
1.2
6
5
4
3
2
1
0
V
and Buffer ON, Oscillator OFF
REF
Serial Data Clocked During the 48 Clock
Count Conversion Cycle, CCLK = SCLK
1
0.8
0.6
V
V
= 5 V
= 3 V
DD
DD
0.4
0.2
0
1
10
100
1
2
4
5
8
10
16
20
Sampling Rate − ksps
Gain
Figure 7
Figure 8
8
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
INPUT BIAS CURRENT
vs
INPUT VOLTAGE
0.6
0.5
0.4
0.3
Input Impedance Inversely
Proportional to Sampling Rate
V
DD
= 5 V
V
DD
= 3 V
0.2
0.1
0
−0.1
−0.2
−0.3
−0.4
0
1
2
3
4
5
6
V − Input Voltage − V
I
Figure 9
INTEGRAL LINEARITY ERROR
2
1.5
1
0.5
0
−0.5
−1
−1.5
−2
0
1024
2048
3072
4096
Output Code
Figure 10
DIFFERENTIAL LINEARITY ERROR
2
1.5
1
0.5
0
−0.5
−1
0
1024
2048
3072
4096
Output Code
Figure 11
9
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
OVERVIEW
The ADS7870 is a complete data acquisition device composed of an input analog multiplexer (MUX), a
programmable gain amplifier (PGA) and an analog-to-digital (A/D) converter. Four lines of digital input/output
(I/O) are also provided. Additional circuitry provides support functions including conversion clock, voltage
reference, and serial interface for control and data retrieval.
Control and configuration of the ADS7870 are accomplished by command bytes written to internal registers
through the serial port. Command register device control includes MUX channel selection, PGA gain, A/D start
conversion command, and I/O line control. Command register configuration control includes internal voltage
reference setting and oscillator control.
Operational modes and selected functions can be activated by digital inputs at corresponding pins. Pin settable
configuration options include SCLK active-edge selection, master reset, and internal oscillator clock enable.
The ADS7870 has eight analog signal input pins, LN0 through LN7. These pins are connected to a network of
analog switches (the MUX). The inputs can be configured as 8 single-ended or 4 differential inputs, or some
combination.
The four general-purpose digital I/O pins (I/O3 through I/O0) can be made to function individually as either digital
inputs or digital outputs. These pins give the user access to four digital I/O pins through the serial interface
without having to run additional wires to the host controller.
The programmable gain amplifier (PGA) provides gains of 1, 2, 4, 5, 8, 10, 16, and 20 V/V.
The 12-bit A/D converter in the ADS7870 is a successive approximation type. The default output of the
converter is 2s complement format and can be read in a variety of ways depending on the program
configuration.
The ADS7870 internal voltage reference can be software configured for output voltages of 1.15 V, 2.048 V, or
2.5 V. The reference circuit is trimmed for high initial accuracy and low temperature drift. A separate buffer
amplifier is provided to buffer the high impedance VREF output.
The voltage reference, PGA, and A/D converter use the conversion clock (CCLK) and signals derived from it.
CCLK can be either an input or output signal. The ADS7870 can divide the CCLK signal by a constant before
it is applied to the A/D converter and PGA. This allows a higher frequency system clock to be used to control
the A/D converter operation. Division factors (DF) of 1, 2, 4, and 8 are available. The signal that is actually
applied to the PGA and A/D converter is DCLK, where DCLK = CCLK/DF.
The ADS7870 is designed so that its serial interface can be conveniently used with a wide variety of
microcontrollers. It has four conventional serial interface pins: SCLK (serial data clock), DOUT (serial data out),
DIN (serial data in, which may be set bidirectional in some applications), and CS (chip select function).
The ADS7870 has ten internal user accessible registers which are used in normal operation to configure and
control the device (summarized in Figure 15).
10
ꢀ
ꢁ
ꢂ
ꢃ
ꢄ
ꢃ
ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
FUNCTIONAL DESCRIPTION
Multiplexer
The ADS7870 has eight analog signal input pins, LN0 through LN7. These pins are connected to a network of
analog switches (the MUX block in the block diagram). The switches are controlled by four bits in the Gain/Mux
register.
LN0 through LN7 can be configured as 8 single-ended inputs or 4 differential inputs or some other combination.
Some MUX combination examples are shown in Figure 20. The differential polarity of the input pins can be
changed with the M2 bit in the MUX address. This feature allows reversing the polarity of the conversion result
without having to physically reverse the input connections to the ADS7870.
For linear operation, the input signal at any of the LN0 through LN7 pins can range between GND – 0.2 V and
V
+ 0.2 V. The polarity of the differential signal can be changed through commands written to the Gain/Mux
DD
register, but each line must remain within the linear input common mode voltage range.
Inputs LN0 through LN7 have ESD protection circuitry as the first active elements on the chip. These contain
protection diodes connected to VDD and GND that remain reverse biased under normal operation. If input
voltages are expected beyond the absolute maximum voltage range, it is necessary to add resistance in series
with the input to limit the current to 10 mA or less.
Conversion Clock
The conversion clock (CCLK) and signals derived from it are used by the voltage reference, the PGA, and the
A/D converter. The CCLK pin can be made either an input or an output. For example, one ADS7870 can be
made to be the conversion clock master (CCLK is an output), while the others are slaved to it with their CCLK
pins all being inputs (by default). This can reduce A/D conversion errors caused by multiple clocks and other
systems noise.
When the OSC ENABLE pin is low or zero, the CCLK pin is an input and the ADS7870 relies on an applied external
clock for the conversion process. When OSC ENABLE is high or if the OSCE bit D4 in register 7 is set to a one,
the internal oscillator and an internal buffer is enabled, making pin 19 an output. Either way the CCLK is sensed
internally at the pin so all ADS7870s see the same clock delays. Capacitive loading on the CCLK pin can draw
significant current compared with the supply current to the ADS7870 (I
= f
× V
× C
).
LOAD
CCLK
DD
LOAD
The internal reference requires a continuous clock and may be supplied by the internal oscillator independently
of the system clock driving the CCLK pin. Setting OSCR (bit D5 in register 7) and REFE (bit D3 in register 7)
both to one accomplishes this. Figure 12 illustrates all of these relationships.
The ADS7870 utilizes the power saving technique of turning on and off the biasing for the PGA and A/D as
needed. This does not apply to the oscillator, reference, and buffer, these run continuously when enabled. The
buffer output is high impedance when disabled, so for a low power data logging application the filter capacitor
is not discharged when the buffer is turned off, and does not require as much settling time when turned on.
The serial interface clock is independent of the conversion clock and can run faster or slower. If it is desirable
to use a faster system clock than the 2.5-MHz nominal rate that the ADS7870 uses then this clock may be
divided to a slower rate ( 1/2, 1/4, 1/8) by setting the appropriate bits in register 3. This clock divider applies
equally to an external as well as internal clock to create the internal DCLK for the PGA and A/D conversion cycle.
The ADS7870 has both maximum and minimum DCLK frequency constraints (DCLK = CCLK/DF). The
maximum DCLK is 2.5 MHz. The minimum DCLK frequency applied to the PGA, reference, and A/D is 100 kHz.
11
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Pin 28
BUFOUT/REFIN
Pin 26
VREF
Pin 27
BUFIN
Internal Oscillator
(2.5 MHz)
REF
BUF
Enabled by
Enabled by
Reg.7 D2,
BUFE
To ADC
Reg.7 D4, OSCE or
Reg.7D5, OSCR or
Pin 18, OSC Enable
OSC CLK
Reg.7 D5
OSCR = 1
Enabled by
Pin 18 OSC Enable
Reg.7 D4, OSCE
Internal
Pin 18
OSC
ENABLE
Reference
1/4
Enabled by
Reg.7D3,
REFE
Reg.7 D5
OSCR = 0
1/N Divider
Pin 19
CCLK
DCLK
N Set by
Reg.3 D[1:0],
CFD[1:0]
Internal Control
Logic
ADS7870
Figure 12. Block Diagram With Internal and External Clocks and References
Voltage Reference and Buffer Amplifier
The ADS7870 uses a patented switched capacitor implementation of a band-gap reference. The circuit has
curvature correction for drift and can be software configured for output voltages of 1.15 V, 2.048 V, or 2.5 V
(default). The internal reference output (VREF) is not designed to drive a typical load; a separate buffer amplifier
must be used to supply any load current.
The internal reference buffer (REFBUF) can source many tens of milliamps to quickly charge a filter capacitor
tied to its output, but it can only typically sink 200 µA. If there is any significant noise on the REFIN pin, then
a resistor to ground (≥ 250 Ω) would improve the buffers ability to recover from a positive going noise spike.
This would, of course, be at the expense of power dissipation.
The temperature compensation of the onboard reference is adjusted with the reference buffer in the circuit.
Performance is specified in this configuration.
Programmable Gain Amplifier
The programmable gain amplifier (PGA) provides gains of 1, 2, 4, 5, 8, 10, 16, and 20 V/V. The PGA is a single
supply, rail-to-rail input, auto-zeroed, capacitor based instrumentation amplifier. PGA gain is set by bits G2
through G0 of register 4.
The ability to detect when the PGA outputs are driven to clipping, or nonlinear operation, is provided by the least
significant bit of the output data (register 0) being set to one. This result is the logical OR of fault detecting
comparators within the ADS7870 monitoring the outputs of the PGA. The inputs are also monitored, for
problems, often due to ac common mode or low supply operation and ORed to this OVL bit. Register 2 can be
read to determine what fault conditions existed during the conversion. The OVL bit also facilitates a quick test
to allow for an auto-ranging application, indicating to the system controller it should try reducing the PGA gain.
12
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
A/D Converter
The 12-bit A/D converter in the ADS7870 is a successive approximation type. The output of the converter is
2s complement format and can be read through the serial interface MSB first or LSB first. A plot of output codes
vs input voltage is shown in Figure 13. With the input multiplexer configured for differential input, the A/D
transfer function is:
* VREF
VREF * 1 LSB
* 2048 v Code v 2047for
v VIN
v
G
G
(1)
(2)
With the input multiplexer configured for single-ended inputs, the A/D transfer function is:
VREF * 1 LSB
0 v Code v 2047for 0 v VIN
v
G
Positive Full Scale Transition
0111 1111 1111 (2047)
0111 1111 1110 (2046)
Output Code is 2s Complement
0000 0000 0010 (2)
0000 0000 0001 (1)
0000 0000 0000 (0)
–V
REF
Zero Transition
+V
REF
1111 1111 1111 (−1)
1111 1111 1110 (−2)
1000 0000 0001 (−8191)
1000 0000 0001 (−8192)
Negative Full Scale Transition
INPUT VOLTAGE
Figure 13. Output Codes Versus Input Voltage
13
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Conversion Cycle
A conversion cycle requires 48 DCLKs, where DCLK = CCLK/DF, the divided−down clock. Operation of the
PGA requires 36 DCLKs: capture the input signal, auto-zero the PGA, level-shift and amplify the input signal.
The period of this cycle makes certain the settling time is sufficient for gain = 20 and (source impedance of 2
kΩ or less) even if the gain is less than 20. The SAR converter takes the last 12 DCLKs.
For maximum sampling rate the input command and output data must be communicated during this cycle,
although this is not recommended for best performance.
During the conversion cycle the internal capacitive load at the selected MUX input changes between 6 pF and
9.7 pF. When the ADS7870 is not converting, the MUX inputs have a nominal 4-pF load capacitance.
The source impedance of the input causes the voltage to vary on the DCLK transitions as the internal capacitors
are switched in and out. A 10-nF to 100-nF capacitor across the differential inputs helps filter these glitches
and act as an antialias filter in combination with the source impedance. Source impedance greater than 2 kΩ
requires longer settling times and so CCLK should be reduced accordingly.
For minimum power dissipation, the bias needed for each function is turned on, allowed to settle, and run only
for the duration required for each conversion. Low rate data logging applications can capitalize on this by
utilizing the internal oscillator as needed rather than running a slow system clock.
Starting an A/D Conversion Cycle
There are four ways to cause the ADS7870 to perform a conversion:
1. Send a direct mode instruction.
The next conversion queues up, waiting for the
current conversion to complete
2. Write to register 4 with the CNV bit = 1
3. Write to register 5 with the CNV bit = 1
4. Assert the CONVERT pin (logic high) —
}
A new conversion cycle starts at the second active
edge of CCLK.
Serial Interface
The ADS7870 communicates with microprocessors and other external circuitry through a digital serial port
interface. It is compatible with a wide variety of popular microcontrollers and digital signal processors (DSP).
These include TI’s TMS320, MSC1210, and MSP430 product families. Other vendors products such as
Motorola 68HC11, Intel 80C51, and MicroChip PIC Series are also supported.
The serial interface consists of four primary pins, SCLK (serial bit clock), DIN (serial data input), DOUT (serial
data output) and CS (chip select). SCLK synchronizes the data transfer with each bit being transmitted on the
falling or rising SCLK edge as determined by the RISE/FALL pin. SDIN may also be used as a serial data output
line.
Additional pins expand the versatility of the basic serial interface and allow it to be used with different
microcontrollers. The BUSY pin indicates when a conversion is in progress and may be used to generate
interrupts for the microcontroller. The CONVERT pin can be used as a hardware-based method of causing the
ADS7870 to start a conversion cycle. The RESET pin can be toggled in order to reset the ADS7870 to the
power-on state.
Communication through the serial interface is dependent on the microcontroller providing an instruction byte
followed by either additional data (for a write operation) or just additional SCLKs to allow the ADS7870 to provide
data (for a read operation). Special operating modes for reducing the instruction byte overhead for retrieving
conversion results are available.
Reset of device (RESET), start of conversion (CONVERT), and oscillator enable (OSC ENABLE) can be done
by signals to external pins or entries to internal registers. The actual execution of each of these commands is
a logical OR function; either pin or register signal TRUE causes the function to execute. The CONVERT pin
signal is an edge-triggered event, with a hold time of two CCLK periods for debounce.
14
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Operating Modes
The ADS7870 serial interface operates based on an instruction byte followed by an action commanded by the
contents of that instruction. The 8-bit instruction word is clocked into the DIN input. There are two types of instruction
bytes that may be written to the ADS7870 as determined by bit D7 of the instruction word (see Figure 14). These
two instructions represent two different operating modes. In direct mode (bit D7 = 1), a conversion is started. A
register mode (bit D7 = 0) instruction is followed by a read or write operation to the specified register.
INSTRUCTION BYTE
D7 (MSB) D6
D5
D4
D3
D2
D1
D0
Start Conversion
(Direct Mode)
1
G2
G1
G0
M3
M2
M1
M0
OR
A4
Read/Write
(Register Mode)
0
R/W
16/8
A3
A2
A1
A0
(1)
START CONVERSION INSTRUCTION BYTE (Direct Mode)
BIT
D7
SYMBOL
NAME
VALUE
FUNCTION
Starts a conversion cycle (direct mode)
Mode select
PGA gain select
1
D6−D4
G2−G0
000
001
010
011
100
101
110
111
PGA Gain = 1 (power up default condition)
PGA Gain = 2
PGA Gain = 4
PGA Gain = 5
PGA Gain = 8
PGA Gain = 10
PGA Gain = 16
PGA Gain = 20
D3−D0
M3−M0
Input channel select
See Figure 21 Determines input channel selection for the requested conversion,
differentialor single-ended configuration.
(1)
The seven lower bits of this byte are also written to register 4, the Gain/Mux register.
READ/WRITE INSTRUCTION BYTE (Register Mode)
BIT
D7
D6
SYMBOL
NAME
VALUE
FUNCTION
Mode Select
0
Initiates a read or write operation (register mode)
R/W
16/8
Read/Write Select
0
1
Write operation
Read operation
D5
Word Length
0
1
8-Bit word
16-Bit word (2 8-bit bytes)
D4−D0 AS4−AS0
Register Address
See Figure 15 Determines the address of the register that is to be read from or written to
Figure 14. Instruction Byte Addressing
Direct Mode
In direct mode a conversion is initiated by writing a single 8-bit instruction byte to the ADS7870 (bit D7 is set
to 1). Writing the direct mode command sets the configuration of the multiplexer, selects the gain of the PGA,
and starts a conversion cycle. After the last bit of the instruction byte is received, the ADS7870 performs a
conversion on the selected input channel with the PGA gain set as indicated in the instruction byte.
The conversion cycle begins on the second falling edge of DCLK after the eighth active edge of SCLK of the
instruction byte. When the conversion is complete, the conversion result is stored in the A/D output registers
and is available to be clocked out of the serial interface by the controlling device using the READ operation in
the register mode.
The structure of the instruction byte for direct mode is shown in Figure 14.
D
D
D7: This bit is set to 1 for direct mode operation
D6 through D4 (G2 − G0): These bits control the gain of the programmable gain amplifier. PGA gains of 1,
2, 4, 5, 8, 10,16, and 20 are available. The coding is shown in Figure 14.
D
D3 through D0 (M3 − M0): These bits configure the switches that determine the input channel selection.
The input channels may be placed in either differential or single-ended configurations. In the case of
differential configuration, the polarity of the input signal is reversible. The coding is shown in Figure 21.
15
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Note that the seven lower bits of this byte are written to register 4, the Gain/Mux register.
All other controllable ADS7870 parameters are values previously stored in their respective registers. These
values are either the power-up default values (0) or values that were previously written to one of the control
registers in a register mode operation. No additional data is required for a direct mode instruction.
Register Mode
In register mode (Bit D7 of the Instruction Byte is 0) a read or write instruction to one of the ADS7870’s registers
is initiated. All of the user determinable functions and features of the ADS7870 can be controlled by writing
information to these registers (see Figure 15). Conversion results can be read from the A/D Output registers.
REGISTER ADDRESS
REGISTER CONTENT
D7
ADDR READ/
(MSB)
A4
A3
A2
A1
A0
D6
D5
D4
D3
D2
D1
D0
NO.
WRITE
REGISTER NAME
A/D Output Data,
LS Byte
0
0
0
0
0
0
Read
ADC3
ADC2
ADC1
ADC0
0
0
0
OVR
A/D Output Data,
MS Byte
0
0
0
0
1
1
Read
ADC11 ADC10
ADC9
ADC8
ADC7
ADC6
ADC5
ADC4
0
0
0
0
0
0
1
1
0
1
2
3
Read
R/W
0
0
0
0
VLD5
BIN
VLD4
0
VLD3
VLD2
VLD1
CFD1
VLD0
CFD0
PGA Valid Register
A/D Control Register
RMB1
RBM0
CNV/
BSY
0
0
0
0
0
0
0
0
1
1
1
1
0
0
1
1
0
1
0
1
4
5
6
7
R/W
R/W
R/W
R/W
G2
0
G1
G0
M3
IO3
M2
IO2
M1
IO1
M0
IO0
Gain/Mux Register
CNV/
BSY
Digital I/O State
Register
0
0
0
0
Digital I/O Control
Register
0
0
0
OE3
REFE
OE2
BUFE
OE1
R2V
OE0
RBG
Ref/Oscillator
Control Register
0
OSCR
OSCE
Serial Interface
Control Register
1
1
1
1
0
1
0
1
0
1
24
31
R/W
LSB
0
2W/3W
0
8051
0
0
0
0
0
8501
0
2W/3W
0
LSB
1
Read
ID Register
Figure 15. Register Address Map
The instruction byte (see Figure 14) contains the address of the register for the next read/write operation,
determines whether the serial communication is to be done in 8-bit or 16-bit word length, and determines
whether the next operation is read-from or written-to the addressed register.
The structure of the instruction byte for register mode is shown in Figure 14.
D
D7: This bit is set to 0 for register mode operation.
D
D6 (R/W): Bit 6 of the instruction byte determines whether a read or write operation is performed, 1 for
a read or 0 for a write.
D
D
D5 (16/8): This bit determines the word length of the read or write operation that follows, 1 for sixteen bits
(two eight-bit bytes) or 0 for eight bits.
D4 through D0 (A4 − A0): These bits determine the address of the register that is to be read from or written
to. Register address coding and other information are tabulated in Figure 15.
For sixteen-bit operations, the first eight bits is written-to/read-from the address encoded by the instruction byte,
bits A4 through A0 (register address). The address of the next eight bits depends upon whether the register
address for the first byte is odd or even. If it is even, then the address for the second byte is the register address
+ 1. If the register address is odd, then the address for the second byte is the register address – 1.
This arrangement allows transfer of conversion results from the two A/D Output Data registers either MS byte
first or LS byte first (refer to the section Serial Interface Control Register).
Register Summary
A summary of information about the addressable registers is shown in Figure 15. Their descriptions follow, and
more detailed information is provided later in the section Internal User-Accessible Registers.
Registers 0 and 1, the A/D Output Data registers, contain the least significant and most significant bits of the
A/D conversion result (ADC0 through ADC13). Register 0 also has three fixed zeros (D3, D2, and D1), and a
bit to indicate if the internal voltage limits of the PGA have been over ranged (OVR). This is a read only register.
Write an 8-bit word to register 0 and the ADS7870 resets.
16
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Register 2, the PGA Valid register, contains information that describes the nature of the problem in the event
that the allowable input voltage to the PGA has been exceeded.
Register 3, the A/D Control register, has two test bits (best left set to zero), a bit to convert the output format
to straight binary (BIN), an unused bit set to zero, two bits to configure an automatic read back mode of the A/D
results (RBM1, RBM0), and two bits that program the frequency divider for the CCLK (CDF1, CDF0).
Register 4, the Gain/Mux register, contains the input channel selection information (M0 through M3) and the
programmable gain amplifier gain set bits (G0 through G2).
Register 5, the Digital I/O State register, contains the state of each of the digital I/O pins (I/O3 through I/O0).
In addition, registers 4 and 5 contain a convert/busy bit (CNV/BSY) that can be used to start a conversion via
a write instruction or sense when the converter is busy with a read instruction.
Register 6, the Digital I/O Control register, contains the information that determines whether each of the four
digital I/O pins is to be an input or an output function (OE3 through OE0). This sets the mode of each I/O pin.
Register 7, the Ref/Oscillator Control register, controls whether the internal oscillator used for the conversion
clock is on or off (OSCE), whether the internal voltage reference and buffer are on or off (REFE, BUFE), and
whether the reference provides 2.5 V, 2.048 V, or 1.15 V.
Register 24, the Serial Interface Control register, controls whether data is presented MSB or LSB first (LSB bit),
whether the serial interface is configured for 2-wire or 3-wire operation (2W/3W bit), and determines proper
timing control for 8051-type microprocessor interfaces (8051 bit).
Register 31, the ID register, is read only.
Reset
There are three ways to reset.
All register contents and the serial interface are reset on:
1. Cycle power. The power down time must be long enough to allow internal nodes to discharge.
2. Toggle the RESET pin. Minimum pulse width to reset is 50 ns.
3. Write an 8-bit byte to register 0. The ADS7870 does not wait for the data which would normally follow this
instruction.
All of these actions set all internal registers to zero, turns off the oscillator, reference, and buffer. Recovery time
for the reference is dependent on capacitance on the reference and buffer outputs.
Only the serial interface is reset (and disabled) when the CS signal is brought high. If CS is continuously held
low, and the ADS7870 is reset by an 8-bit write to register 0 (even if inadvertently) then the next 1 input to DIN
is the synchronizing bit for the serial interface. The next active edge of SCLK following this 1 latches in the first
bit of the new instruction byte.
For applications where CS cannot be cycled, and system synchronization is lost, the ADS7870 must be reset
by writing 39 zeros and a one. The serial interface is then ready to accept the next command byte. This string
length is based on the worst case conditions to ensure that the device is synchronized.
NOTE:
A noisy SCLK, with excessive ringing, can cause the ADS7870 to inadvertently reset. Sufficient capacitance to
correct this problem may be provided by just a scope probe, which would mask this issue during debugging. A
100-Ω capacitor in series with the SCLK pin is usually sufficient to correct this problem. Since the data is changed
on the opposite edge of SCLK, it is usually settled before the active edge of SCLK and would not need its own 100-Ω
resistor, although it would not be detrimental.
17
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Write Operation
To perform a write operation an instruction byte must first be written to the ADS7870 as described previously
(see Figure 14). This instruction determines the target register as well as the word length (8 bits or 16 bits). The
CS pin must be asserted (0) prior to the first active SCLK edge (rising or falling depending on the state of the
RISE/FALL pin) that latches the first bit of the instruction byte. The first active edge after CS must have the first
bit of the instruction byte. The remaining seven bits of the instruction byte are latched on the next seven active
edges of SCLK. CS must remain low for the entire sequence. Setting CS high resets the serial interface.
When starting a conversion by setting the CNV/BSY bit in the Gain/Mux register and/or the Digital I/O register,
the conversion starts on the second falling edge of DCLK after the last active SCLK edge of the write operation.
Figure 16 shows an example of an eight-bit write operation with LSB first and SCLK active on the rising edge.
The double arrows indicate the SCLK transition when data is latched into its destination register.
Instruction Latched
Register is updated
SCLK
DIN
A0
A1
A2
A3
A4
0
0
D0
D1
D2
D3
D4
D7
0
D5
D6
DOUT
CS
Figure 16. Timing Diagram for an 8-Bit Write Operation
Figure 17 shows an example of the timing for a 16-bit write to an even address with LSB first and SCLK active
on the rising edge. Notice that both bytes are updated to their respective registers simultaneously. Also shown
is that the address (ADDR) for the write of the second byte is incremented by one since the ADDR in the
instruction byte was even. For an odd ADDR, the address for the second byte would be ADDR−1.
Instruction Latched
Both Bytes Updated
SCLK
DIN
0
A1 A2 A3 A4
1
0
0
D7 D0
D0 D1 D2 D3 D4 D5 D6
Data for ADDR
D1 D2
D3 D4 D5 D6 D7
Data for ADDR + 1
DOUT
CS
Figure 17. Timing Diagram of a 16-Bit Write Operation to an Even Address
18
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Read Operation
A read operation is similar to a write operation except that data flow (after the instruction byte) is from the
ADS7870 to the host controller. After the instruction byte has been latched (on the eighth active edge of SCLK),
the DOUT pin (and the DIN pin if in two-wire mode) begins driving data on the next nonactive edge of SCLK.
This allows the host controller to have valid data on the next active edge of SCLK.
The data on DOUT (or DIN) transitions on the nonactive edges of SCLK. The DIN pin (two-wire mode) ceases
driving data (return to high impedance) on the nonactive edge of SCLK following the eighth (or sixteenth) active
edge of the read data. DOUT is only high impedance when CS is not asserted. With CS high (1), DOUT (or
DIN) is forced to high impedance mode. In general, the ADS7870 is insensitive to the idle state of the clock
except that the state of SCLK may determine if DIN is driving data or not.
Upon completion of the read operation, the ADS7870 is ready to receive the next instruction byte. Read
operations reflect the state of the ADS7870 on the first active edge of SCLK of the data byte transferred.
Figure 18 shows an example of an eight-bit read operation with LSB first and SCLK active on the rising edge.
The double rising arrows indicate when the instruction is latched.
SCLK
A0
A2
1
0
A1
0
A3
A4
DIN
D5
D0
D1
D2
D6
D7
D3
D4
DOUT
CS
Figure 18. Timing Diagram for an 8-Bit Read Operation
Figure 19 provides an example of a 16-bit read operation from an odd address with LSB first and SCLK active
on the rising edge. The address (ADDR) for the second byte is decremented by one since the ADDR in the
instruction byte is odd. For an even ADDR, the address for the second byte would be incremented by one.
SCLK
A3
1
A1 A2
1
1
0
A4
DIN
D7
D0 D1 D2 D3
Data from ADDR
D6
D0
D1 D2 D3 D4
D5 D6
D7
D4 D5
DOUT
Data from ADDR−1
CS
Figure 19. Timing Diagram for a 16-Bit Read Operation to an Odd Address
19
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Multiplexer Addressing
The last four bits in the instruction byte (during a start conversion instruction) or the Gain/Mux register (ADDR
= 4) assign the multiplexer configuration for the requested conversion. The input channels may be placed in
either differential or single-ended configurations. For differential configurations, the polarity of the input signal
is reversible by the state of M2 (Bit D2). In single-ended mode, all input channels are measured with respect
to system ground (pin 25). Figure 20 shows some examples of multiplexer assignments and Figure 21 provides
the coding for the input channel selection.
EXAMPLES OF MULTIPLEXER OPTIONS
Differential and
4 Differential
8 Single−Ended
Single−Ended
Channel
Channel
Channel
+
–
+
+
LN0
LN1
LN0, LN1
LN0, LN1
–
+
+
+
+
+
+
+
LN2
LN3
+
–
–
+
LN2, LN3
LN4, LN5
LN6, LN7
LN2, LN3
LN4
LN4
LN5
LN6
LN7
+
+
+
+
–
+
LN5
LN6
–
+
LN7
Figure 20. Examples of Multiplexer Options
CODING FOR SINGLE-ENDED INPUT CHANNEL SELECT
(negative input is ground)
CODING FOR DIFFERENTIAL INPUT CHANNEL SELECT
SELECTION BITS
INPUT LINES
SELECTION BITS
INPUT LINES
LN3 LN4
M3
0
M2
0
M1
0
M0
0
LN0
+
LN1
−
LN2
+
LN3
LN4
LN5
−
LN6
LN7
M3
1
M2
0
M1
0
M0
0
LN0
+
NL1
+
LN2
LN5
LN6
LN7
0
0
0
1
−
1
0
0
1
0
0
1
0
+
1
0
1
0
+
0
0
1
1
+
−
1
0
1
1
+
0
1
0
0
−
+
1
1
0
0
+
0
1
0
1
−
+
1
1
0
1
+
0
1
1
0
−
+
1
1
1
0
+
0
1
1
1
−
+
1
1
1
1
+
NOTE:
Bit M3 selects either differential or single-ended mode. If differential mode is selected, bit M2 determines the polarity of the input channels.
Bold items are power-up default conditions.
Figure 21. Multiplexer Addressing
20
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
INTERNAL USER-ACCESSIBLE REGISTERS
The registers in the ADS7870 are eight bits wide. Most of the registers are reserved, the ten user-accessible
registers are summarized in the register address map (see Figure 15). Detailed information for each register
follows. The default power-on/reset state of all bits in the registers is 0.
ADC Output Registers
The A/D output registers are read only registers located at ADDR = 0 and ADDR = 1 that contain the results
of the A/D conversion, ADC11 through ADC0 (see Figure 22). The conversion result is in 2s complement
format. The bits can be taken out of the registers MSB (D7) first or LSB (D0) first, as determined by the state
of the LSB bits (D7 or D0) in the Serial Interface Control register. The ADDR = 0 register also contains the OVR
bit which indicates if the internal voltage limits to the PGA have been exceeded.
ADC OUTPUT REGISTERS
ADDR
D7 (MSB)
ADC3
D6
D5
D4
D3
0
D2
0
D1
0
D0
0
1
ADC2
ADC10
ADC1
ADC9
ADC0
ADC8
OVR
ADC4
ADC11
ADC7
ADC6
ADC5
ADDR = 0 (LS Byte)
BIT
SYMBOL
NAME
VALUE
FUNCTION
ADC3−
ADC0
D7−D4
A/D Output
(1)
0
Four least significant bits of conversion result
D3−D1
D0
—
—
These bits are not used and are always 0.
Valid conversion result
An analog over-range problem has occurred in the PGA. Conversion result may
be invalid. Details of the type of problem are stored in register 2, the PGA Valid
register.
OVR
PGA Over-Range
0
1
ADDR = 1 (MS Byte)
BIT
SYMBOL
NAME
VALUE
(1)
FUNCTION
D7−D0
ADC11−
ADC4
ADC Output
Eight most significant bits of conversion result
(1)
Value depends on conversion result.
Figure 22. ADC Output Registers (ADDR = 0 and ADDR = 1)
21
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
PGA Valid Register
The PGA Valid register (ADDR = 2) is a read only register that contains the individual results of each of the six
comparators for the PGA, VLD5 through VLD0, as shown in Figure 23.
PGA VALID REGISTER
ADDR
D7 (MSB)
D6
D5
D4
D3
D2
D1
D0
2
0
0
VLD5
VLD4
VLD3
VLD2
VLD1
VLD0
ADDR = 2
BIT
SYMBOL
NAME
VALUE
FUNCTION
D7−D6
D5
—
—
0
These bits are not used and are always 0.
VLD5
PGA Valid 5
0
1
0 − Voltage at minus (−) output from the PGA is within its minimum value.
1 − Voltage at minus (−) output from the PGA has exceeded its minimum value.
D4
D3
D2
D1
D0
VLD4
VLD3
VLD2
VLD1
VLD0
PGA Valid 4
PGA Valid 3
PGA Valid 2
PGA Valid 1
PGA Valid 0
0
1
0 − Voltage at minus (−) output from the PGA is within its maximum value.
1 − Voltage at minus (−) output from the PGA has exceeded its maximum value.
0
1
0 − Voltage at minus (−) input to the PGA is within its maximum value.
1 − Voltage at minus (−) input to the PGA has exceeded its maximum value.
0
1
0 − Voltage at plus (+) output from the PGA is within its minimum value.
1 − Voltage at plus (+) output from the PGA has exceeded its minimum value.
0
1
0 − Voltage at plus (+) output from the PGA is within its maximum value.
1 − Voltage at plus (+) output from the PGA has exceeded its maximum value.
0
1
0 − Voltage at plus (+) input to the PGA is within its maximum value.
1 − Voltage at plus (+) input to the PGA has exceeded its maximum value.
Bold items are power-up default conditions.
Figure 23. PGA Valid Register (ADDR = 2)
22
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
A/D Control Register
The A/D Control register (ADDR = 3) configures the CCLK divider and read back mode option as shown in
Figure 24.
ADC CONTROL REGISTER
ADDR
D7 (MSB)
D6
D5
D4
D3
D2
D1
D0
3
0
0
BIN
0
RBM1
RBM0
CFD1
CFD0
ADDR = 3
BIT
SYMBOL
—
NAME
VALUE
FUNCTION
D7−D6
D5
—
0
These bits are reserved and must always be written 0.
BIN
Output Data
Format
0
1
Mode 0 − Twos complement output data format
Mode 1 − Binary output data format
D4
—
—
0
This is a reserved bit and must always be written 0.
D3−D2
RBM1−RBM0
Automatic Read
Back Mode
00
01
10
11
Mode 0 − Read instruction required to access ADC conversion result.
Mode 1 − Most significant byte returned first
Mode 2 − Least significant byte returned first
Mode 3 − Only most significant byte returned
D1−D0
CFD1−CFD0
CCLK Divide
00
01
10
11
Division factor for CCLK = 1 (DCLK = CCLK)
Division factor for CCLK = 2 (DCLK = CCLK/2)
Division factor for CCLK = 4 (DCLK = CCLK/4)
Division factor for CCLK = 8 (DCLK = CCLK/8)
Bold items are power-up default conditions.
Figure 24. ADC Control Register (ADDR = 3)
Read Back Modes
RBM1 and RBM0 determine which of four possible modes is used to read the A/D conversion result from the
A/D Output registers.
D
D
Mode 0 (default mode) requires a separate read instruction to be performed in order to read the output
of the A/D Output registers
Mode 1, 2, and 3: Provide for different types of automatic read-back options of the conversion results from
the A/D Output registers without having to use separate read instructions:
Mode 1: Provides data MS byte first
Mode 2: Provides data LS byte first
Mode 3: Output only the MS byte
For more information refer to the Read Back Mode section.
Clock Divider
CFD1 and CFD0 set the CCLK divisor constant which determines the DCLK applied to the A/D, PGA, and
reference. The A/D and PGA operate with a maximum clock of 2.5 MHz. In situations where an external clock
is used to pace the conversion process it may be desirable to reduce the external clock frequency before it is
actually applied to the PGA and A/D. The signal that is actually applied to the A/D and PGA is called DCLK,
where DCLK = CCLK/DF (DF is the division factor determined by the CFD1 and CFD0 bits). For example, if
the external clock applied to CCLK is 10 MHz and DF = 4 (CFD1 = 1, CFD0 = 0), DCLK equals 2.5 MHz.
23
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Gain/Mux Register
The Gain/Mux register (ADDR = 4) contains the bits that configure the PGA gain (G2 − G0) and the input channel
selection (M3 − M0) as shown in Figure 25. This register is also updated when direct mode is used to start a
conversion so its bit definition is compatible with the instruction byte.
GAIN/MUX REGISTER
ADDR
D7 (MSB)
D6
D5
D4
D3
D2
D1
D0
4
CNV/BSY
G2
G1
G0
M3
M2
M1
M0
ADDR = 4
BIT
SYMBOL
NAME
VALUE
FUNCTION
D7
CNV/BSY
Convert/Busy
0
1
Idle Mode
Busy Mode; write = start conversion
D6−D4
D3−D0
G2−G0
PGA Gain Select
000
001
010
011
100
101
110
111
PGA Gain = 1
PGA Gain = 2
PGA Gain = 4
PGA Gain = 5
PGA Gain = 8
PGA Gain = 10
PGA Gain = 16
PGA Gain = 20
M3−M0
Input Channel Select
See
Determines input channel selection for the requested conversion, differential or
Figure 21 single-ended configuration.
Bold items are power-up default conditions.
Figure 25. Gain/Mux Register (ADDR = 4)
Input Channel Selection
Bits M3 through M0 configure the switches that determine the input channel selection. The input channels may
be placed in either differential or single-ended configurations. In the case of differential configuration, the
polarity of the input pins is reversible by the state of the M2 bit. The coding for input channels is given in Figure 21
and examples of different input configurations are shown in Figure 20.
Convert/Busy
If the CNV/BSY bit is set to a 1 during a write operation, a conversion starts on the second falling edge of DCLK
after the active edge of SCLK that latched the data into the Gain/Mux register. The CNV/BSY bit may be read
with a read instruction. The CNV/BSY bit is set to 1 in a read operation if the ADS7870 is performing a conversion
at the time the register is sampled in the read operation.
Gain Select
Bits G2 through G0 control the gain of the programmable gain amplifier. PGA gains of 1, 2, 4, 5, 8, 10, 16, and
20 are available. The coding is shown in Figure 25.
24
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Digital Input/Output State Register
The Digital I/O State register (ADDR = 5) contains the state of each of the four digital I/O pins. Each pin can
function as a digital input (the state of the pin is set by an external signal connected to it) or a digital output (the
state of the pin is set by data from a serial input to the ADS7870). The input/output functional control is
established by the digital I/O mode control bits (OE3 − OE0) in the Digital I/O Control register. In addition, the
convert/busy bit (CNV/BSY) can be used to start a conversion via a write instruction or determine if the converter
is busy by executing a read instruction.
Digital I/O State Bits
Bits D3 through D0 (I/O3 − I/O0) of the Digital I/O State register are the state bits. If the corresponding mode
bit makes the pin a digital input, the state bit indicates whether the external signal connected to the pin is a 1
or a 0, and it is not possible to control the state of the corresponding bit with a write operation. The state of the
bit is only controlled by the external signal connected to the digital I/O pin. Coding is shown in Figure 26.
DIGITAL I/O STATE REGISTER
ADDR
D7 (MSB)
D6
D5
D4
D3
D2
D1
D0
5
CNV/BSY
0
0
0
IO3
IO2
IO1
IO0
ADDR = 5
BIT
SYMBOL
NAME
VALUE
FUNCTION
D7
CNV/BSY
Convert/Busy
0
1
Idle Mode
Busy Mode; write = start conversion
D6−D4
D3
—
—
0
These bits are not used and are always 0.
IO3
State for I/O3
0
1
Input or Output State = 0
Input or Output State = 1
D2
D1
D0
IO2
IO1
IO0
State for I/O2
State for I/O1
State for I/O0
0
1
Input or Output State = 0
Input or Output State = 1
0
1
Input or Output State = 0
Input or Output State = 1
0
1
Input or Output State = 0
Input or Output State = 1
Bold items are power-up default conditions.
NOTE:
When the mode control makes a pin a digital input, it is not possible to control the state of the corresponding bit in the Digital I/O State register
with a write operation. The state of the bit is only controlled by the external signal connected to the digital I/O pin.
Figure 26. Digital I/O State Register (ADDR = 5)
The four digital I/O pins allow control of external circuitry, such as a multiplexer, or allow the digital status lines
from other devices to be read without using any additional microcontroller pins. Reads from this register always
reflect the state of the pin, not the state of the latch inside the ADS7870.
Convert/Busy
If CNV/BSY is set to a 1 during a write operation, a conversion starts on the second falling edge of DCLK after
the active edge of SCLK that latched the data into the Digital I/O register. The CNV/BSY bit may be read with
a read instruction. The CNV/BSY bit is set to 1 in a read operation if the ADS7870 is performing a conversion
at the time the register is sampled in the read operation.
25
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Digital I/O Control Register
The Digital I/O Control register (ADDR = 6) contains the information that determines whether each of the four
digital I/O lines is configured as an input or output. Setting the appropriate OE bit to 1 enables the corresponding
I/O pin as an output. Setting the appropriate OE bit to 0 enables the corresponding I/O pin as an input (see
Figure 27).
DIGITAL I/O CONTROL REGISTER
ADDR
D7 (MSB)
D6
D5
D4
D3
D2
D1
D0
6
0
0
0
0
OE3
OE2
OE1
OE0
ADDR = 6
BIT
SYMBOL
NAME
VALUE
FUNCTION
D7−D4
D3
—
—
0
These bits are reserved and must always be set to 0.
OE3
State for I/O3
0
1
Digital I/O 1 − digital input
Digital I/O 1 = digital output
D2
D1
D0
OE2
OE1
OE0
State for I/O2
State for I/O1
State for I/O0
0
1
Digital I/O 2− digital input
Digital I/O 2 − digital output
0
1
Digital I/O 3− digital input
Digital I/O 3 − digital output
0
1
Digital I/O 4− digital input
Digital I/O 4 − digital output
Bold items are power-up default conditions.
Figure 27. Digital I/O Control Register (ADDR = 6)
26
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Reference/Oscillator Configuration Register
The Reference/Oscillator Configuration register (ADDR = 7) determines whether the internal oscillator is used
(OSCE and OSCR), whether the internal voltage reference and buffer are on or off (REFE and BUFE), and
whether the reference is 2.5 V, 2.048 V, or 1.15 V as shown in Figure 28.
REFERENCE/OSCILLATOR REGISTER
ADDR
D7 (MSB)
D6
D5
D4
D3
D2
D1
D0
7
0
0
OSCR
OSCE
REFE
BUFE
R2V
RBG
ADDR = 7
BIT
SYMBOL
NAME
VALUE
FUNCTION
D7−D6
D5
—
—
0
These bits are reserved and must always be set to 0.
Source of clock for internal V is CCLK pin.
OSCR
Oscillator Control
0
1
REF
Clocking signal comes from the internal oscillator.
D4
D3
D2
D1
D0
OSCE
REFE
BUFE
R2V
Oscillator Enable
Reference Enable
Buffer Enable
0
1
CCLK is configured as an input.
CCLK outputs a 2.5-MHz signal (70 µA).
0
1
Reference is powered down.
Reference is powered up.
0
1
Buffer is powered down and draws no current.
Buffer is powered up and draws 150 µA of current.
2-V Reference
0
1
VREF = 2.5 V (RBG bit = 0)
VREF = 2.048 V (RBG bit = 0)
RBG
Bandgap Reference
0
1
Bit R2V determines the value of the reference voltage.
VREF = 1.15 V
Bold items are power-up default conditions.
Figure 28. Reference/Oscillator Configuration Register (ADDR = 7)
Oscillator Control
The internal voltage reference uses a switched capacitor technique which requires a clocking signal input.
When OSCR = 1, the clocking signal for the reference comes from the internal oscillator. When OSCR = 0, the
clocking signal for the reference is derived from the signal on the CCLK pin and affected by the frequency divider
controlled by the CFD0 and CFD1 bits in the A/D Control register.
The OSCE bit is the internal oscillator enable bit. When it is set to 1, power is applied to the internal oscillator
causing it to produce a 2.5-MHz output and causing the signal to appear at the CCLK pin. The internal oscillator
is also enabled when the OSCR bit and the REFE bit are set to 1, but does not make CCLK an output pin.
The internal oscillator is also enabled when the OSC ENABLE pin is set to 1. The power-up default condition
is 0 for OSCE and OSCR. If either the OSC ENABLE pin is held high, or either of these control register bits
are 1, then the oscillator is turned on.
Voltage Reference and Buffer Enable
When the REFE bit = 0 (power-up default condition), the reference is powered down and draws no current.
When REFE is set to 1, the reference is powered up and draws approximately 190 µA of current. When the
BUFE bit = 0 (power-up default condition), the buffer amplifier is powered down and draws no current. When
the buffer amplifier is set to 1, it is powered up and draws approximately 150 µA of current.
Selecting the Reference Voltage
When the RBG bit is set to 1, the voltage on the VREF pin is 1.15 V and the R2V bit has no effect. When this
bit is set to 0 (power-up default condition), the R2V bit determines the value of the reference voltage.
When R2V = 0 and RBG = 0 (power-up default condition), the voltage at the VREF pin is 2.5 V. When R2V =
1 and RBG = 0, the reference voltage is 2.048 V.
A 12-bit bipolar input A/D converter has 4096 states and each state corresponds to 1.22 mV with the 2.5 V
reference. With a 2.048 V reference, each A/D bit corresponds to 1 mV.
27
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Serial Interface Control Register
The Serial Interface Control register (ADDR = 24), see Figure 29, allows certain aspects of the serial interface
to be controlled by the user. It controls whether data is presented MSB or LSB first and whether the serial
interface is configured for 2-wire or 3-wire operation, and it determines proper timing control for 8051-type
microprocessor interfaces.
The information in this register is formatted with the information symmetric about its center. This is done so that
it may be read or written either LSB (bit D7) or MSB (bit D0) first. Each control bit has two locations in the register.
If either of the two is set, the function is activated. This arrangement can potentially simplify microcontroller
communication code.
The instruction byte to write this configuration data to Register 24 is itself symmetric. From Figure 14, a register
mode write instruction of 8 bits to address 24 is 0001 1000 in binary form. Therefore, this command to write
to this register is valid under all conditions.
SERIAL INTERFACE CONTROL REGISTER
ADDR
D7 (MSB)
D6
D5
D4
D3
D2
D1
D0
24
LSB
2W/3W
8051
0
0
8051
2W/3W
LSB
ADDR = 7
BIT
SYMBOL
NAME
VALUE
FUNCTION
D7
LSB
LSB or MSB first
2 Wire or 3 Wire
Serial Interface
0
1
Serial interface receives and transmits MSB first.
Serial interface receives and transmits LSB first.
D6
D5
2W/3W
8051
0
1
3-Wire mode
2-Wire mode
0
DIN high impedance on the next inactive edge or when CS goes inactive.
1
DIN pin is high impedance on last active SCLK edge of the bye of data transfer
D4−D3
D2
—
—
0
These bits are reserved and must always be set 0.
8051
Serial Interface
0
1
DIN high impedance on the next inactive edge or when CS goes inactive.
DIN pin is high impedance on last active SCLK edge of the byte of data transfer
D1
D0
2W/3W
LSB
2 Wire or 3 Wire
LSB or MSB first
0
1
3-Wire mode
2-Wire mode
0
1
Serial interface receives and transmits MSB first.
Serial interface receives and transmits LSB first.
Bold items are power-up default conditions.
Figure 29. Serial Interface Control Register (ADDR = 24)
LSB or MSB
The LSB bit determines whether the serial interface receives and transmits either LSB or MSB first. Setting the
LSB bit (1) configures the interface to expect all bytes LSB first as opposed to the default MSB first (LSB = 0).
2-Wire or 3-Wire Operation
The 2W/3W bit configures the ADS7870 for 2-wire or 3-wire mode. In two-wire mode (2W/3W = 1), the DIN pin
is enabled as an output during the data output portion of a read instruction. The DIN pin accepts data when the
ADS7870 is receiving and it outputs data when the ADS7870 is transmitting. When data is being sent out of
the DIN pin, it also appears on the DOUT pin as well. In three-wire mode (2W/3W = 0), data to the ADS7870
is received on the DIN pin and is transmitted on the DOUT pin. The power-up default condition is three-wire
mode.
28
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Serial Interface Timing (8051 Bit)
The 8051 bit changes the timing of when the DIN pin goes to high impedance at the end of an operation. When
the bit is a 1, the pin goes to high impedance on the last active SCLK edge of the last byte of data transfer instead
of waiting for the next inactive edge, or CS to go inactive. This allows the ADS7870 to disconnect from the data
lines soon enough to avoid contention with an 80C51-type interface. The 80C51 drives data four CPU cycles before
an inactive SCLK edge and for two CPU cycles after an active SCLK edge. When the 8051 bit is a 0, the DIN pin
goes high impedance on the next inactive SCLK edge or when CS goes inactive (1).
Figure 30 and Figure 31 show the timing of when the ADS7870 sets the DIN pin to high impedance at the end
of a read operation when the 2W/3W bit is set. The behavior of DOUT does not depend of the state of 2W/3W.
The 8051 bit is not set for these two examples.
ADS7870 drives DIN
DIN high−impedance on CS
Micro drives DIN
SCLK
0
1
A0
A1
A2
A3
A4
0
D0
D0
D1
D1
D2
D2
D3
D3
D4
D4
D5
D5
D6
D6
D7
D7
DIN
DOUT
CS
Figure 30. Timing for High Impedance State on DIN/DOUT (CS = 1)
ADS7870 drives DIN
DIN high−impedance on inactive edge
Micro drives DIN
SCLK
A1
A0
0
1
D0
D0
D1
D1
D2
D2
D3
D3
D7
D7
A2
D5
D5
D6
D6
A3
A4
0
D4
D4
DIN
DOUT
CS
Figure 31. Timing for High Impedance State on DIN/DOUT (Inactive SCLK Edge)
29
ꢀ
ꢁ
ꢂ
ꢃ
ꢄ
ꢃ
ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Figure 32 shows the timing for entering the high impedance state when the 8051 bit is set. Notice that on the
last bit of the read operation the DIN (and DOUT) pin goes to the high impedance state on the active edge of
SCLK instead of waiting for the inactive edge of SCLK or CS going high as shown in Figure 30 and Figure 31.
This is for compatibility with 80C51 mode 0 type serial interfaces. An 80C51 forces DIN valid before the SCLK
falling edge and holds it valid until after the SCLK rising edge. This can lead to contention but setting the 8051
bit fixes this potential problem without requiring CS to be toggled high after every read operation.
ADS7870 drives DIN
DIN high−impedance on active SCLK edge
Micro drives DIN
SCLK
A0
A1
A2
A3
1
0
D0
D0
D6
D6
D7
A4
0
D1
D1
D2
D2
D4
D4
D5
D5
DIN
D3
D3
DOUT
D7
CS
Figure 32. Timing for High-Impedance State on DIN/DOUT (8051 Bit = 1)
ID Register
The ADS7870 has an ID register (at ADDR = 31) to allow the user to identify which revision of the ADS7870
is installed. This is shown in Figure 33.
ID REGISTER
ADDR
D7 (MSB)
D6
D5
D4
D3
D2
D1
D0
31
0
0
0
0
0
0
0
1
ADDR = 31
BIT
SYMBOL
NAME
VALUE
FUNCTION
D7−D0
—
—
—
The contents of this register identify the revision of the ADS7870
Figure 33. ID Register (ADDR = 31)
Remaining Registers
The remaining register addresses are not used in the normal operation of the ADS7870. These registers return
random values when read and nonzero writes to these registers cause erratic behavior. Unused bits in the
partially used registers must always be written low.
30
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
STARTING A CONVERSION THROUGH THE SERIAL INTERFACE
There are two methods of starting a conversion cycle through the serial interface. The first (nonaddressed or
direct mode) is by using the start conversion byte as described earlier. The second (addressed mode) is by
setting the CNV/BSY bit of register 4 or register 5 by performing a write instruction.
The conversion starts on the second falling edge of DCLK after the eighth active edge of SCLK (for the
instruction in nonaddressed mode or the data in addressed mode). The BUSY pin goes active (1) one DCLK
period (1, 2, 4, or 8 CCLK periods depending on CFD1 and CFD0) after the start of a conversion. This delay
is to allow BUSY to go inactive when conversions are queued to follow in immediate succession. BUSY goes
inactive at the end of the conversion.
If a conversion is already in progress when the CNV/BSY bit is set on the eighth active SCLK edge, the
CNV/BSY bit is placed in the queue and the current conversion is allowed to finish. If a conversion is already
queued, the new one replaces the currently queued conversion. The queue is only one conversion long.
Immediately upon completion of the current conversion, the next conversion starts. This allows for maximum
throughput through the A/D converter. Since BUSY is defined to be inactive for the first DCLK clock period of
the conversion, the inactive (falling) edge of BUSY can be used to mark the end of a conversion (and start of
the next conversion).
Figure 34 shows the timing of a conversion start using the convert start instruction byte. The double rising arrow
on SCLK indicates when the instruction is latched. The double falling arrow on CCLK indicates where the
conversion cycle actually starts (second falling edge of CCLK after the eighth active edge of SCLK). This
example is for LSB first, CCLK divider = 1, and SCLK active on rising edge. Notice that BUSY goes active one
CCLK period later since CCLK divider = 1.
SCLK
M0
M1
M2
M3
G0
G1
1
G2
DIN
DOUT
CS
Conversion Starts
CCLK
BUSY
Figure 34. Timing Diagram for a Conversion Start Using Serial Interface Convert Instruction
31
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Figure 35 shows an example of a conversion start using an 8-bit write operation to the Gain/Mux register with
the CNV/BSY bit set to 1. The double rising arrow on SCLK indicates where the data is latched into the Gain/Mux
register and the double arrow on CCLK indicates when the conversion starts. The example is for LSB first, CCLK
divider = 1, and SCLK active on the rising edge.
SCLK
G2
A1
A2
A3
A4
0
0
0
M0
M1
M2
M3
G0
G1
1
A0
DIN
DOUT
CS
Conversion Starts
CCLK
BUSY
Figure 35. Timing Diagram for a Conversion Start Using 8-Bit Write to the Gain/Mux Register
Figure 36 shows the timing of a conversion start using the convert start instruction byte when a conversion is
already in progress (indicated by BUSY high). The double rising arrow on SCLK indicates when the instruction
is latched. The second falling arrow on CCLK indicates when the conversion cycle would have started had a
conversion not been in progress. The double falling arrow on CCLK indicates where the conversion cycle
actually starts (immediately after completion of the previous conversion). This example is for LSB first, CCLK
divider = 2, and SCLK active on the rising edge. Notice that BUSY is low for two CCLK periods because the
CCLK divider = 2.
SCLK
DIN
M0
M1
G0
G1
1
M2
G2
M3
y
z
DOUT
CS
Normal Start
Delayed Start
CCLK
BUSY
Figure 36. Timing Diagram of Delayed Conversion Start With Serial Interface
32
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
STARTING A CONVERSION USING THE CONVERT PIN
A conversion can also be started by an active (rising) edge on the CONVERT pin. Similar to the CNV/BSY
register bit, the conversion starts on the second falling edge of CCLK after the CONVERT rising edge.
The CONVERT pin must stay high for at least two CCLK periods. CONVERT must also be low for at least two
CCLK periods before going high. BUSY goes active one DCLK period after the start of the conversion.
Contrary to the CNV/BSY bit in the register, the CONVERT pin aborts any conversion in process and
restarts a new conversion. BUSY goes low at the end of the conversion. CS may be either high or low when
the CONVERT pin starts a conversion.
Figure 37 shows the timing of a conversion start using the CONVERT pin. The double falling arrow on CCLK
indicates when the conversion cycle actually starts (the second active CCLK edge after CONVERT goes
active). This example is for CCLK divider = 4. Notice that BUSY goes active four CCLK periods later.
Conversion Starts
CCLK
BUSY
CONV
Figure 37. Timing Diagram of Conversion Start Using CONVERT Pin
READ BACK MODES
There are four modes available to read the A/D conversion result from the A/D Output registers. The RBM1 and
RBM0 bits in the A/D Control register (ADDR = 3) control which mode is used by the ADS7870.
Read Back Mode 0 (default mode) requires a separate read instruction to retrieve the conversion result
Read Back Mode 1 (automatic) provides the output most significant byte first
Read Back Mode 2 (automatic) provides the output least significant byte first
Read Back Mode 3 (automatic) provides only the most significant byte
Mode 3 does not short cycle the A/D. Automatic read back mode is only triggered when starting a conversion
using the serial interface. Conversions started using the CONVERT pin do not trigger the read back mode.
The first bit of data for an automatic read back is loaded on the first active SCLK edge of the read portion of
instruction. The remaining bits are loaded on the next inactive SCLK edge (the first one after the first active
edge). To avoid getting one bit from one conversion and the remainder of the byte from another conversion,
a conversion should not finish between the first active SCLK edge and the next inactive edge.
Mode 0
Mode 0 (default operating mode) requires a read instruction to be performed to retrieve a conversion result.
MS byte first format is achieved by performing a sixteen bit read from ADDR = 1. LS byte first format is achieved
by performing a sixteen bit read from ADDR = 0. Reading only the most significant byte can be achieved by
performing an eight bit read from ADDR = 1.
To increase throughput it is possible to read the result of a conversion while a conversion is in progress. The
last conversion completed prior to the first active SCLK edge of the conversion data word (not the instruction
byte) is retrieved. This overlapping allows a sequence of start conversion N, read conversion N – 1, start
conversion N +1, read conversion N, etc. For conversion 0, the result of conversion –1 would need to be
discarded.
33
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
Mode 1
In this mode, the serial interface configures itself to clockout a conversion result as soon as a conversion is
started. This is useful since a read instruction is not required so eight SCLK cycles are saved. This mode
operates like an implied sixteen bit read instruction byte for ADDR = 1 was sent to the ADS7870 after starting
the conversion.
It is not necessary to wait for the end of the conversion to start clocking out conversion results. The last
completed conversion at the sampling edge of SCLK is read back (whether a conversion is in progress or not).
Mode 2
This mode is similar to Mode 1 except that the conversion result is provided LS byte first (equivalent to a sixteen
bit read from ADDR = 0).
Figure 38 and Figure 39 show timing examples of an automatic read back operation using mode 2. In Figure 38,
the result of the previous conversion is retrieved. This example is for LSB first, CCLK divider = 2, and SCLK
active on the rising edge. The data may be read back immediately after the start conversion instruction. It is
not necessary to wait for the conversion to actually start (or finish).
First output bit loaded in the output register
The remaining output bits loaded in the output register
SCLK
DIN
M0 M1
M3 G0 G1
1
M2
G2
DOUT
OVR
0
0
0
B0 B1 B2 B3
B4 B5 B6 B7 B8 B9 B10 B11
CS
CCLK
BUSY
Figure 38. Timing Diagram for Automatic Read Back of Previous Conversion Result Using Mode 2
34
ꢀ ꢁꢂ ꢃꢄ ꢃꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
In Figure 39 the result of the just requested conversion is retrieved. The microcontroller must wait for BUSY
to go inactive before clocking out the ADC Output register. CS must stay low while waiting for BUSY. This
example is for LS byte first, CCLK divider = 1, and SCLK active on the falling edge. Notice that the DOUT pin
is not driven with correct data until the appropriate active edge of SCLK.
SCLK
DIN
1
G2 G1 G0 M3 M2 M1 M0
B3 B2 B1 B0
0
0
0
OVR B11 B10 B9 B8
B7 B6 B5 B4
DOUT
CS
CCLK
BUSY
Figure 39. Timing Diagram for Automatic Read Back of Current Conversion Result Using Mode 2
Mode 3
This mode only returns the most significant byte of the conversion. It is equivalent to an eight bit read from
ADDR = 1.
35
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
APPLICATION INFORMATION
REQUIRED SUPPORT ELEMENTS
As with any precision analog integrated circuit, good power supply bypassing is required. A low ESR ceramic
capacitor in parallel with a large value electrolytic capacitor across the supply line furnishes the required
performance. Typical values are 0.1 µF and 10 µF respectively. Noise performance of the internal voltage
reference circuit is improved if a ceramic capacitor of approximately 0.01 µF is connected from VREF to ground.
Increasing the value of this capacitor may bring slight improvement in the noise on VREF but increases the time
required to stabilize after turn on.
If the internal buffer amplifier is used, it must have an output filter capacitor connected to ground to ensure
stability. A nominal value of 0.47 µF provides the best performance. Any value between 0.1 µF and 10 µF is
acceptable. In installations where one ADS7870 buffer is used to drive several devices, an additional filter
capacitor of 0.1 µF should be installed at each of the slave devices.
The circuit in Figure 40 shows a typical installation with all control functions under control of the host embedded
controller. The SCLK is active on the falling edge. If the internal voltage reference and oscillator are used, they
must be turned on by setting the corresponding control bits in the device registers. These registers must be
set on power up and after any reset operation.
VDD
ADS7870
0.01 µF
10 µF
24
25
RESET
VDD
GND
RISE/FALL
23
11
12
13
14
I/O0
CS
I/O1
I/O2
I/O3
20
21
22
SCLK
DIN
Serial Interface
Digital I/O − 4 Lines
DOUT
1
2
3
4
5
6
7
8
LN0
LN1
LN2
LN3
LN4
LN5
LN6
18
19
16
17
26
27
28
15
OSC_ENABLE
CCLK
CONVERT
BUSY
VREF
BUFIN
0.01 µF
BUFOUT/ REFIN
NC
LN7
0.47 µF
Analog In − 8 Lines
Figure 40. Typical Operation With Recommended Capacitor Values
36
ꢀ
ꢁ
ꢂ
ꢃ
ꢄ
ꢃ
ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
APPLICATION INFORMATION
MICROCONTROLLER CONNECTIONS
The ADS7870 is quite flexible in interfacing to various microcontrollers. Connections using the hardware mode
of two types of controllers (Motorola M68HC11, Intel 80C51) are described below.
Motorola M68HC11 (SPI)
The Motorola M68HC11 has a three-wire (four if you count the slave select) serial interface that is commonly
referred to as SPI (serial peripheral interface), where the data is transmitted MSB first. This interface is usually
described as the microcontroller and the peripheral each having two 8-bit shift registers (one for receiving and
one for transmitting).
The transmit shift register of the microcontroller and the receive shift register of the peripheral are connected
together and vice versa. SCK controls the shift registers. SPI is capable of full duplex operation (simultaneous
read and write). The ADS7870 does not support full duplex operation. The ADS7870 can only be written to
or read from. It cannot do both simultaneously.
Since the M68HC11 can configure SCK to have either rising or falling edge active, the RISE/FALL pin on the
ADS7870 can be in whichever state is appropriate for the desired mode of operation of the M68HC11 for
compatibility with other peripherals.
In the Interface Control register (see Figure 29), the 2W/3W bit should be cleared (default). The LSB bit should
be clear (default). The 8051 bit should also be clear (default). Since the ADS7870 defaults to SPI mode, the
M68HC11 should not need to initialize the ADS7870 Interface Configuration register after power-on or reset.
Figure 41 shows a typical physical connection between an M68HC11 and a ADS7870. A pull-up resister on
DOUT may be needed to keep DOUT from floating during write operations. CS may be permanently tied low
if desired, but then the ADS7870 must be the only peripheral.
V
DD
10 kΩ typ
ADS7870
M68HC11
MISO
MOSI
SCK
SS
DIN
DOUT
SCLK
CS
Figure 41. Connection of a M68HC11 to an ADS7870
37
ꢀꢁ ꢂꢃ ꢄ ꢃ ꢅ
www.ti.com
SBAS124C − DECEMBER 1999 − REVISED DECEMBER 2005
APPLICATION INFORMATION
Intel 80C51
The Intel 80C51 operated in serial port mode 0 has a two-wire (three-wire if an additional I/O pin is used for CS)
serial interface. The TXD pin provides the clock for the serial interface and RXD serves as the data input and
output. The data is transferred LSB first. Best compatibility is achieved by connecting the RISE/FALL pin of the
ADS7870 high (rising edge of SCLK active). In the Interface Configuration register, the LSB bit and the 8051
bit should be set. The 2W/3W bit should also be set. The first instruction after power-on or reset should
be a write operation to the Interface Configuration register.
Figure 42 shows a typical physical connection between an 80C51 and an ADS7870. CS may be permanently
tied low if desired, but then the ADS7870 must be the only peripheral.
V
DD
10 kΩ typ
80C51
RXD
ADS7870
DIN
DOUT
SCLK
CS
TXD
Px.x
Figure 42. Connection of an 80C51 to an ADS7870
38
PACKAGE OPTION ADDENDUM
www.ti.com
28-Mar-2008
PACKAGING INFORMATION
Orderable Device
ADS7870EA
Status (1)
ACTIVE
ACTIVE
ACTIVE
ACTIVE
Package Package
Pins Package Eco Plan (2) Lead/Ball Finish MSL Peak Temp (3)
Qty
Type
Drawing
SSOP
DB
28
28
28
28
50 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
ADS7870EA/1K
ADS7870EA/1KG4
ADS7870EAG4
SSOP
SSOP
SSOP
DB
DB
DB
1000 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
1000 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
50 Green (RoHS & CU NIPDAU Level-1-260C-UNLIM
no Sb/Br)
(1) The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check
http://www.ti.com/productcontent for the latest availability information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and
package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS
compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame
retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
30-Jan-2009
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0 (mm)
B0 (mm)
K0 (mm)
P1
W
Pin1
Diameter Width
(mm) W1 (mm)
(mm) (mm) Quadrant
ADS7870EA/1K
SSOP
DB
28
1000
330.0
16.4
8.2
10.5
2.5
12.0
16.0
Q1
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
30-Jan-2009
*All dimensions are nominal
Device
Package Type Package Drawing Pins
SSOP DB 28
SPQ
Length (mm) Width (mm) Height (mm)
346.0 346.0 33.0
ADS7870EA/1K
1000
Pack Materials-Page 2
MECHANICAL DATA
MSSO002E – JANUARY 1995 – REVISED DECEMBER 2001
DB (R-PDSO-G**)
PLASTIC SMALL-OUTLINE
28 PINS SHOWN
0,38
0,22
0,65
28
M
0,15
15
0,25
0,09
5,60
5,00
8,20
7,40
Gage Plane
1
14
0,25
A
0°–ā8°
0,95
0,55
Seating Plane
0,10
2,00 MAX
0,05 MIN
PINS **
14
16
20
24
28
30
38
DIM
6,50
5,90
6,50
5,90
7,50
8,50
7,90
10,50
9,90
10,50 12,90
A MAX
A MIN
6,90
9,90
12,30
4040065 /E 12/01
NOTES: A. All linear dimensions are in millimeters.
B. This drawing is subject to change without notice.
C. Body dimensions do not include mold flash or protrusion not to exceed 0,15.
D. Falls within JEDEC MO-150
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements,
and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should
obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are
sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard
warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where
mandated by government requirements, testing of all parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and
applications using TI components. To minimize the risks associated with customer products and applications, customers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right,
or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information
published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a
warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual
property of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied
by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive
business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional
restrictions.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all
express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not
responsible or liable for any such statements.
TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably
be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing
such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products
and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be
provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in
such safety-critical applications.
TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are
specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military
specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at
the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use.
TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are
designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated
products in automotive applications, TI will not be responsible for any failure to meet such requirements.
Following are URLs where you can obtain information on other Texas Instruments products and application solutions:
Products
Amplifiers
Applications
Audio
Automotive
Broadband
Digital Control
Medical
Military
Optical Networking
Security
amplifier.ti.com
dataconverter.ti.com
www.dlp.com
www.ti.com/audio
Data Converters
DLP® Products
DSP
Clocks and Timers
Interface
www.ti.com/automotive
www.ti.com/broadband
www.ti.com/digitalcontrol
www.ti.com/medical
www.ti.com/military
www.ti.com/opticalnetwork
www.ti.com/security
www.ti.com/telephony
www.ti.com/video
dsp.ti.com
www.ti.com/clocks
interface.ti.com
logic.ti.com
power.ti.com
microcontroller.ti.com
www.ti-rfid.com
Logic
Power Mgmt
Microcontrollers
RFID
Telephony
Video & Imaging
Wireless
RF/IF and ZigBee® Solutions www.ti.com/lprf
www.ti.com/wireless
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2009, Texas Instruments Incorporated
相关型号：
ADS7870IDB
12-BIT, 52-kSPS, DATA ACQUISITION SYSTEM WITH ANALOG-TO-DIGITAL CONVERTER, MUX, PGA, AND REFERENCE
TI
ADS7870IDBR
12-BIT, 52-kSPS, DATA ACQUISITION SYSTEM WITH ANALOG-TO-DIGITAL CONVERTER, MUX, PGA, AND REFERENCE
TI
ADS7871
14-BIT, 48-KSPS, DATA ACQUISITION SYSTEM WITH ANALOG-TO-DIGITAL CONVERTER, MUX, PGA, AND REFERENCE
TI
ADS7871IDB
14-BIT, 48-KSPS, DATA ACQUISITION SYSTEM WITH ANALOG-TO-DIGITAL CONVERTER, MUX, PGA, AND REFERENCE
TI
ADS7871IDBG4
14-BIT, 48-KSPS, DATA ACQUISITION SYSTEM WITH ANALOG-TO-DIGITAL CONVERTER, MUX, PGA, AND REFERENCE
TI
ADS7871IDBR
14-BIT, 48-KSPS, DATA ACQUISITION SYSTEM WITH ANALOG-TO-DIGITAL CONVERTER, MUX, PGA, AND REFERENCE
TI
ADS7871IDBRG4
14-BIT, 48-KSPS, DATA ACQUISITION SYSTEM WITH ANALOG-TO-DIGITAL CONVERTER, MUX, PGA, AND REFERENCE
TI
ADS7881
16-BIT, 1-MSPS, PSEUDO-BIPOLAR, FULLY DIFFERENTIAL INPUT, MICROPOWER SAMPLING ANALOG-TO-DIGITAL CONVERTER WITH PARALLEL INTERFACE, REFERENCE
BB
©2020 ICPDF网 联系我们和版权申明