AD5781BRUZ-REEL7 [ADI]
True 18-Bit, Voltage Output DAC ±0.5 LSB INL, ±0.5 LSB DNL; 真正的18位电压输出DAC A ±0.5 LSB INL ，A ±0.5 LSB DNL
| 型号： | AD5781BRUZ-REEL7 |
| 厂家： | 
ADI |
| 描述： | True 18-Bit, Voltage Output DAC ±0.5 LSB INL, ±0.5 LSB DNL |
| 文件： | 总28页 (文件大小：854K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
True 18-Bit, Voltage Output DAC
0.5 LSB INL, 0.5 LSB DNL
Data Sheet
AD5781
FEATURES
FUNCTIONAL BLOCK DIAGRAM
V
V
V
V
CC
DD
REFPF REFPS
Single 18-bit DAC, 0.5 LSB INL
7.5 nV/√Hz noise spectral density
0.05 LSB long-term linearity stability
<0.05 ppm/°C temperature drift
1 µs settling time
1.4 nV-sec glitch impulse
Operating temperature range: −40°C to +125°C
20-lead TSSOP package
6.8kΩ 6.8kΩ
R1
AD5781
A1
R
IOV
CC
FB
R
FB
INV
SDIN
SCLK
SYNC
SDO
INPUT
SHIFT
18
18
18-BIT
DAC
DAC
REG
V
OUT
REGISTER
AND
CONTROL
LOGIC
6kΩ
LDAC
Wide power supply range of up to 16.5 V
35 MHz Schmitt triggered digital interface
1.8 V compatible digital interface
CLR
POWER-ON-RESET
AND CLEAR LOGIC
RESET
DGND
V
AGND
V V
REFNF REFNS
APPLICATIONS
SS
Figure 1.
Medical instrumentation
Test and measurement
Industrial control
Table 1. Complementary Devices
Part No.
Description
Scientific and aerospace instrumentation
Data acquisition systems
Digital gain and offset adjustment
Power supply control
AD8675
Ultraprecision, 36 V, 2.8 nV/√Hz rail-to-rail
output op amp
Ultraprecision, 36 V, 2.8 nV/√Hz dual rail-to-
rail output op amp
AD8676
ADA4898-1
High voltage, low noise, low distortion, unity
gain stable, high speed op amp
Table 2. Related Devices
Part No.
Description
AD5791
20-bit, 1 ppm accurate DAC
AD5541A/AD5542A 16-bit, 1 LSB accurate 5 V DAC
GENERAL DESCRIPTION
The AD57811 is a single 18-bit, unbuffered voltage output DAC
that operates from a bipolar supply of up to 33 V. The AD5781
accepts a positive reference input range of 5 V to VDD − 2.5 V and
a negative reference input range of VSS + 2.5 V to 0 V. The
AD5781 offers a relative accuracy specification of 0.5 LSB
maximum, and operation is guaranteed monotonic with a 0.5
LSB DNL maximum specification.
PRODUCT HIGHLIGHTS
1. True 18-Bit Accuracy.
2. Wide Power Supply Range of Up to 16.5 V.
3. −40°C to +125°C Operating Temperature Range.
4. Low 7.5 nV/√Hz Noise.
5. Low 0.05 ppm/°C Temperature Drift.
The part uses a versatile 3-wire serial interface that operates at
clock rates of up to 35 MHz and is compatible with standard
SPI, QSPI™, MICROWIRE™, and DSP interface standards. The
part incorporates a power-on reset circuit that ensures that the
DAC output powers up to 0 V and in a known output impedance
state and remains in this state until a valid write to the device
takes place. The part provides an output clamp feature that
places the output in a defined load state.
1 Protected by U.S. Patent No 7884747, and other patents are pending.
Rev. D
Document Feedback
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rights of third parties that may result fromits use. Specifications subject to change without notice. No
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Tel: 781.329.4700 ©2010–2013 Analog Devices, Inc. All rights reserved.
Technical Support
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AD5781
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
DAC Architecture....................................................................... 19
Hardware Control Pins.............................................................. 20
On-Chip Registers...................................................................... 21
AD5781 Features ............................................................................ 24
Power-On to 0 V......................................................................... 24
Configuring the AD5781 .......................................................... 24
DAC Output State ...................................................................... 24
Linearity Compensation............................................................ 24
Output Amplifier Configuration.............................................. 24
Applications Information .............................................................. 26
Typical Operating Circuit ......................................................... 26
Evaluation Board ........................................................................ 26
Outline Dimensions....................................................................... 27
Ordering Guide .......................................................................... 27
Applications....................................................................................... 1
Functional Block Diagram .............................................................. 1
General Description ......................................................................... 1
Product Highlights ........................................................................... 1
Revision History ............................................................................... 2
Specifications..................................................................................... 3
Timing Characteristics ................................................................ 5
Absolute Maximum Ratings............................................................ 7
ESD Caution.................................................................................. 7
Pin Configuration and Function Description .............................. 8
Typical Performance Characteristics ............................................. 9
Terminology .................................................................................... 17
Theory of Operation ...................................................................... 19
REVISION HISTORY
7/13—Rev. C to Rev. D
8/11—Rev. 0 to Rev. A
Changes to t1 Test Conditions/Comments and Endnote 2 ......... 5
Deleted Figure 4................................................................................ 7
Deleted Daisy-Chain Operation Section..................................... 20
Change to Features Section..............................................................1
Changes to Specifications Section...................................................3
Deleted t14 Parameter from Timing Specifications Section,
Table 4 .................................................................................................5
Changes to Figure 2 and Figure 3....................................................6
Changes to Figure 4...........................................................................7
Replaced Figure 42 and Figure 43................................................ 16
Added New Figure 44, Figure 45, and Figure 46, Renumbered
Sequentially ..................................................................................... 16
11/11—Rev. B to Rev. C
Added Figure 48; Renumbered Sequentially .............................. 17
Change to Ideal Transfer Function Equation.............................. 22
9/11—Rev. A to Rev. B
Added Patent Note ........................................................................... 1
Changes to Table 3............................................................................ 3
Changes to OPGND Description, Table 12 ................................ 23
7/10—Revision 0: Initial Version
Rev. D | Page 2 of 28
Data Sheet
AD5781
SPECIFICATIONS
VDD = +12.5 V to +16.5 V, VSS = −16.5 V to −12.5 V, V REFP = +10 V, VREFN = −10 V, VCC = +2.7 V to +5.5 V, IOV CC = +1.71 V to +5.5 V,
RL = unloaded, CL = unloaded, TMIN to TMAX, unless otherwise noted.
Table 3.
A, B Version1
Parameter
Min
Typ
Max
Unit
Test Conditions/Comments
STATIC PERFORMANCE2
Resolution
Integral Nonlinearity Error (Relative
Accuracy)
18
−0.5
Bits
LSB
0.25
+0.5
B version, VREFP = +10 V, VREFN = −10 V
−0.5
−1
−4
−0.5
−0.5
−1
0.25
0.5
2
0.25
0.25
0.5
0.04
0.05
0.03
0.25
0.062 +2.75
+0.5
+1
+4
+0.5
+0.5
+1
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
LSB
B version, VREFP = +10 V, VREFN = 0 V3
B version, VREFP = +5 V, VREFN = 0 V3
A version4
VREFP = +10 V, VREFN = −10 V
VREFP = +10 V, VREFN = 0 V3
VREFP = +5 V, VREFN = 0 V3
After 500 hours at TA = 125°C
After 1000 hours at TA = 125°C
After 1000 hours t TA = 100°C
VREFP = +10 V, VREFN = −10 V3
VREFP = +10 V, VREFN = 0 V3
VREFP = +5 V, VREFN = 0 V3
Differential Nonlinearity Error
Linearity Error Long-Term Stability5
Full-Scale Error
−1.75
−2.75
−5.25
−1
+1.75
0.2
0.25
+5.25
+1
VREFP = +10 V, VREFN = −10 V3,
TA = 0°C to 105°C
−1
−1.5
0.062 +1
LSB
LSB
VREFP = 10 V, VREFN = 0 V3, TA = 0°C to 105°C
VREFP = 5 V, VREFN = 0 V3, TA = 0°C to 105°C
0.2
+1.5
Full-Scale Error Temperature Coefficient3
Zero-Scale Error
0.02
0.025 +1.75
0.38
0.19
0.025 +1
ppm FSR/°C
LSB
LSB
LSB
LSB
−1.75
−2.5
−5.25
−1
VREFP = +10 V, VREFN = −10 V3
VREFP = +10 V, VREFN = 0 V3
VREFP = +5 V, VREFN = 0 V3
VREFP = +10 V, VREFN = −10 V3,
TA = 0°C to 105°C
+2.5
+5.25
−1
−1.5
0.38
0.19
0.04
0.3
0.4
0.4
+1
+1.5
LSB
LSB
VREFP = 10 V, VREFN = 0 V3, TA = 0°C to 105°C
VREFP = 5 V, VREFN = 0 V3, TA = 0°C to 105°C
Zero-Scale Error Temperature Coefficient3
Gain Error
ppm FSR/°C
ppm FSR
ppm FSR
ppm FSR
ppm FSR/°C
%
−6
−10
−20
+6
+10
+20
VREFP = +10 V, VREFN = −10 V3
VREFP = +10 V, VREFN = 0 V3
VREFP = +5 V, VREFN = 0 V3
Gain Error Temperature Coefficient3
R1, RFB Matching
OUTPUT CHARACTERISTICS3
0.04
0.01
Output Voltage Range
VREFN
VREFP
V
Output Slew Rate
Output Voltage Settling Time
50
1
V/µs
µs
Unbuffered output, 10 MΩ||20 pF load
10 V step to 0.02%, using AD845
buffer in unity-gain mode
125 code step to 1 LSB6
1
µs
Output Noise Spectral Density
Output Voltage Noise
7.5
7.5
7.5
1.1
nV/√Hz
nV/√Hz
nV/√Hz
µV p-p
at 1 kHz, DAC code = midscale
at 10 kHz, DAC code = midscale
at 100 kHz, DAC code = midscale
DAC code = midscale, 0.1 Hz to
10 Hz bandwidth7
Rev. D | Page 3 of 28
AD5781
Data Sheet
A, B Version1
Parameter
Min
Typ
3.1
1.7
1.4
9.1
3.6
1.9
45
Max
Unit
Test Conditions/Comments
Midscale Glitch Impulse
nV-sec
nV-sec
nV-sec
nV-sec
nV-sec
nV-sec
nV-sec
nV-sec
kΩ
VREFP = +10 V, VREFN = −10 V
VREFP = +10 V, VREFN = 0 V
VREFP = +5 V, VREFN = 0 V
VREFP = +10 V, VREFN = −10 V, see Figure 42
VREFP = 10 V, VREFN = 0 V, see Figure 43
VREFP = 5 V, VREFN = 0 V, see Figure 44
On removal of output ground clamp
MSB Segment Glitch Impulse6
Output Enabled Glitch Impulse
Digital Feedthrough
DC Output Impedance (Normal Mode)
DC Output Impedance (Output
Clamped to Ground)
0.4
3.4
6
kΩ
Spurious Free Dynamic Range
Total Harmonic Distortion
REFERENCE INPUTS3
100
97
dB
dB
1 kHz tone, 10 kHz sample rate
1 kHz tone, 10 kHz sample rate
VREFP Input Range
VREFN Input Range
DC Input Impedance
5
VDD − 2.5 V
0
V
VSS + 2.5 V
5
6.6
15
kΩ
pF
VREFP, VREFN, code dependent,
typical at midscale code
Input Capacitance
VREFP, VREFN
LOGIC INPUTS3
Input Current8
−1
+1
0.3 × IOVCC
µA
V
V
Input Low Voltage, VIL
Input High Voltage, VIH
IOVCC = 1.71 V to 5.5 V
IOVCC = 1.71 V to 5.5 V
0.7 × IOVCC
Pin Capacitance
5
pF
LOGIC OUTPUT (SDO)3
Output Low Voltage, VOL
Output High Voltage, VOH
High Impedance Leakage Current
High Impedance Output Capacitance
0.4
1
V
IOVCC = 1.71 V to 5.5 V, sinking 1 mA
IOVCC = 1.71 V to 5.5 V, sourcing 1 mA
IOVCC − 0.5 V
µA
pF
3
POWER REQUIREMENTS
All digital inputs at DGND or IOVCC
VDD
VSS
VCC
7.5
VDD − 33
2.7
VSS + 33
−2.5
5.5
V
V
V
IOVCC
1.71
5.5
V
IOVCC ≤ VCC
IDD
ISS
ICC
IOICC
4.2
4
5.2
4.9
900
140
mA
mA
µA
µA
µV/V
µV/V
dB
dB
600
52
0.6
0.6
95
95
SDO disabled
VDD 10%, VSS = 15 V
VSS 10%, VDD = 15 V
VDD 200 mV, 50 Hz/60 Hz, VSS = −15 V
VSS 200 mV, 50 Hz/60 Hz, VDD = 15 V
DC Power Supply Rejection Ratio3, 9
AC Power Supply Rejection Ratio3
1 Temperature range: −40°C to +125°C, typical conditions: TA = 25°C, VDD = +15 V, VSS = −15 V, VREFP = +10 V, VREFN = −10 V.
2 Performance characterized with AD8676BRZ voltage reference buffers and AD8675ARZ output buffer.
3 Linearity error refers to both INL error and DNL error; either parameter can be expected to drift by the amount specified after the length of time specified.
4 Valid for all voltage reference spans.
5 Guaranteed by design and characterization, not production tested.
6 The AD5781 is configured in the bias compensation mode with a low-pass RC filter on the output. R = 300 Ω, C = 143 pF (total capacitance seen by the output buffer,
lead capacitance, and so forth).
7 Includes noise contribution from AD8676BRZ voltage reference buffers.
8 Current flowing in an individual logic pin.
9 Includes PSRR of AD8676BRZ voltage reference buffers.
Rev. D | Page 4 of 28
Data Sheet
AD5781
TIMING CHARACTERISTICS
VCC = 2.7 V to 5.5 V; all specifications TMIN to TMAX, unless otherwise noted.
Table 4.
Limit1
Parameter
IOVCC = 1.71 V to 3.3 V
IOVCC = 3.3 V to 5.5 V Unit
Test Conditions/Comments
SCLK cycle time
SCLK cycle time (readback mode)
SCLK high time
2
t1
40
92
15
9
28
60
10
5
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns min
ns typ
ns typ
ns min
ns typ
ns min
t2
t3
t4
SCLK low time
5
5
SYNC to SCLK falling edge setup time
SCLK falling edge to SYNC rising edge hold time
Minimum SYNC high time
t5
2
2
t6
48
8
40
6
t7
SYNC rising edge to next SCLK falling edge ignore
Data setup time
Data hold time
LDAC falling edge to SYNC falling edge
SYNC rising edge to LDAC falling edge
LDAC pulse width low
t8
t9
9
7
7
12
13
20
14
130
130
50
140
0
t10
t11
t12
t13
t14
t15
t16
t17
t18
t19
t20
t21
t22
10
16
11
130
130
50
140
0
LDAC falling edge to output response time
SYNC rising edge to output response time (LDAC tied low)
CLR pulse width low
CLR pulse activation time
SYNC falling edge to first SCLK rising edge
65
62
0
60
45
0
ns max SYNC rising edge to SDO tristate (CL = 50 pF)
ns max SCLK rising edge to SDO valid (CL = 50 pF)
ns min
ns typ
ns typ
SYNC rising edge to SCLK rising edge ignore
RESET pulse width low
35
150
35
150
RESET pulse activation time
1 All input signals are specified with tR = tF = 1 ns/V (10% to 90% of IOVCC) and timed from a voltage level of (VIL + VIH)/2.
2 Maximum SCLK frequency is 35 MHz for write mode and 16 MHz for readback mode.
Rev. D | Page 5 of 28
AD5781
Data Sheet
t1
t7
SCLK
1
2
24
t3
t2
t6
t4
t5
SYNC
SDIN
t9
t8
DB23
DB0
t12
t10
t11
LDAC
t13
V
V
OUT
OUT
t14
t15
CLR
t16
V
OUT
t21
RESET
t22
V
OUT
Figure 2. Write Mode Timing Diagram
t20
t1
t17
t7
SCLK
1
2
24
1
2
24
t3
t2
t6
t17
t5
t5
t4
SYNC
SDIN
t9
t8
DB23
DB0
INPUT WORD SPECIFIES
REGISTER TO BE READ
NOP CONDITION
t18
t19
DB23
DB0
SDO
REGISTER CONTENTS CLOCKED OUT
Figure 3. Readback Mode Timing Diagram
Rev. D | Page 6 of 28
Data Sheet
AD5781
ABSOLUTE MAXIMUM RATINGS
TA = 25°C, unless otherwise noted. Transient currents of up to
100 mA do not cause SCR latch-up.
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
Table 5.
Parameter
VDD to AGND
VSS to AGND
VDD to VSS
VCC to DGND
IOVCC to DGND
Rating
−0.3 V to +34 V
−34 V to +0.3 V
−0.3 V to +34 V
−0.3 V to +7 V
−0.3 V to VCC + 3 V or +7 V
(whichever is less)
This device is a high performance integrated circuit with an
ESD rating of 1.5 kV, and it is ESD sensitive. Proper precautions
should be taken for handling and assembly.
Digital Inputs to DGND
−0.3 V to IOVCC + 0.3 V or
+7 V (whichever is less)
ESD CAUTION
VOUT to AGND
VREFPF to AGND
VREFPS to AGND
VREFNF to AGND
VREFNS to AGND
DGND to AGND
−0.3 V to VDD + 0.3 V
−0.3 V to VDD + 0.3 V
−0.3 V to VDD + 0.3 V
VSS − 0.3 V to +0.3 V
VSS − 0.3 V to +0.3 V
−0.3 V to +0.3 V
Operating Temperature Range, TA
Industrial
Storage Temperature Range
Maximum Junction Temperature,
TJ max
−40°C to + 125°C
−65°C to +150°C
150°C
Power Dissipation
TSSOP Package
(TJ max − TA)/θJA
θJA Thermal Impedance
θJC Thermal Impedance
Lead Temperature
Soldering
143°C/W
45°C/W
JEDEC industry standard
J-STD-020
ESD (Human Body Model)
1.5 kV
Rev. D | Page 7 of 28
AD5781
Data Sheet
PIN CONFIGURATION AND FUNCTION DESCRIPTION
1
2
20
19
18
17
16
15
14
13
12
11
INV
OUT
R
FB
V
AGND
3
V
V
REFPS
SS
AD5781
TOP VIEW
(Not to Scale)
4
V
V
REFPF
REFNS
5
V
V
REFNF
DD
6
RESET
CLR
DGND
SYNC
SCLK
SDIN
SDO
7
8
LDAC
9
V
CC
CC
10
IOV
Figure 4. Pin Configuration
Table 6. Pin Function Descriptions
Pin No.
Mnemonic
Description
1
2
3
INV
VOUT
VREFPS
Connection to Inverting Input of External Amplifier. See the AD5781 Features section for further details.
Analog Output Voltage.
Positive Reference Sense Voltage Input. A voltage range of 5 V to VDD − 2.5 V can be connected. A unity gain amplifier
must be connected at this pin, in conjunction with the VREFPF pin. See the AD5781 Features section for further details.
4
5
VREFPF
VDD
Positive Reference Force Voltage Input. A voltage range of 5 V to VDD − 2.5 V can be connected. A unity gain amplifier
must be connected at these pin, in conjunction with the VREFPS pin. See AD5781 Features section for further details.
Positive Analog Supply Connection. A voltage range of 7.5 V to 16.5 V can be connected. VDD should be decoupled to
AGND.
6
7
Active Low Reset Logic Input Pin. Asserting this pin returns the AD5781 to its power-on status.
RESET
CLR
Active Low Clear Logic Input Pin. Asserting this pin sets the DAC register to a user defined value (see Table 13) and
updates the DAC output. The output value depends on the DAC register coding that is being used, either binary or twos
complement.
8
Active Low Load DAC Logic Input Pin. This is used to update the DAC register and, consequently, the analog output.
When tied permanently low, the output is updated on the rising edge of SYNC. If LDAC is held high during the write
cycle, the input register is updated, but the output update is held off until the falling edge of LDAC. The LDAC pin
should not be left unconnected.
LDAC
9
VCC
Digital Supply Connection. A voltage in the range of 2.7 V to 5.5 V can be connected. VCC should be decoupled to DGND.
10
IOVCC
Digital Interface Supply Pin. Digital threshold levels are referenced to the voltage applied to this pin. A voltage range of
1.71 V to 5.5 V can be connected. IOVCC should not be allowed to exceed VCC.
11
12
SDO
SDIN
Serial Data Output Pin. Data is clocked out on the rising edge of the serial clock input.
Serial Data Input Pin. This device has a 24-bit shift register. Data is clocked into the register on the falling edge of the
serial clock input.
13
14
SCLK
SYNC
Serial Clock Input. Data is clocked into the input shift register on the falling edge of the serial clock input. Data can be
transferred at clock rates of up to 35 MHz.
Active Low Digital Interface Synchronization Input Pin. This is the frame synchronization signal for the input data. When
SYNC is low, it enables the input shift register, and data is then transferred in on the falling edges of the following clocks.
The input shift register is updated on the rising edge of SYNC.
15
16
DGND
VREFNF
Ground Reference Pin for Digital Circuitry.
Negative Reference Force Voltage Input. A voltage range of VSS + 2.5 V to 0 V can be connected. A unity gain amplifier
must be connected at this pin, in conjunction with the VREFNS pin. See the AD5781 Features section for further details.
17
18
VREFNS
VSS
Negative Reference Sense Voltage Input. A voltage range of VSS + 2.5 V to 0 V can be connected. A unity gain amplifier
must be connected at these pin, in conjunction with the VREFNF pin. See the AD5781 Features section for further details.
Negative Analog Supply Connection. A voltage range of −16.5 V to −2.5 V can be connected. VSS should be decoupled to
AGND.
19
20
AGND
RFB
Ground Reference Pin for Analog Circuitry.
Feedback Connection for External Amplifier. See the AD5781 Features section for further details.
Rev. D | Page 8 of 28
Data Sheet
AD5781
TYPICAL PERFORMANCE CHARACTERISTICS
0.5
0.5
0.4
T
T
T
= +125°C
= +25°C
= –40°C
T
T
T
= +25°C
= –40°C
= +125°C
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
A
A
A
A
A
A
0.4
V
V
V
V
= +10V
= 0V
= +15V
REFP
REFN
0.3
0.3
DD
SS
0.2
0.2
= –15V
0.1
0.1
0
0
–0.1
–0.2
–0.3
–0.4
–0.5
–0.1
–0.2
–0.3
–0.4
–0.5
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
V
V
V
V
= +10V
= –10V
= +15V
= –15V
50000
REFP
REFN
DD
SS
0
100000
150000
200000
250000
0
50000
100000
150000
200000
250000
DAC CODE
DAC CODE
Figure 5. Integral Nonlinearity Error vs. DAC Code, 10 V Span
Figure 8. Integral Nonlinearity Error vs. DAC Code, 10 V Span, X2 Gain Mode
0.5
0.5
T
T
T
= +125°C
= +25°C
= –40°C
T
T
T
= +125°C
= +25°C
= –40°C
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
A
A
A
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
A
A
A
0.4
0.3
0.4
0.3
V
V
V
V
= +10V
= –10V
= +15V
REFP
REFN
DD
SS
0.2
0.2
= –15V
0.1
0.1
0
0
–0.1
–0.2
–0.3
–0.4
–0.5
–0.1
–0.2
–0.3
–0.4
–0.5
V
V
V
V
= +10V
= 0V
= +15V
REFP
REFN
DD
SS
= –15V
0
50000
100000
150000
200000
250000
0
50000
100000
150000
200000
250000
DAC CODE
DAC CODE
Figure 6. Integral Nonlinearity Error vs. DAC Code, +10 V Span
Figure 9. Differential Nonlinearity Error vs. DAC Code, 10 V Span
1.0
0.5
T
T
T
= +125°C
= +25°C
= –40°C
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
T
T
T
= +125°C
= +25°C
= –40°C
A
A
A
A
A
A
0.8
0.6
0.4
0.3
V
V
V
V
= +10V
= 0V
= +15V
REFP
REFN
DD
SS
0.4
0.2
= –15V
0.2
0.1
0
0
–0.2
–0.4
–0.6
–0.8
–1.0
–0.1
–0.2
–0.3
–0.4
–0.5
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
V
V
V
V
= +5V
= 0V
= +15V
= –15V
REFP
REFN
DD
SS
0
50000
100000
150000
200000
250000
0
50000
100000
150000
200000
250000
DAC CODE
DAC CODE
Figure 7. Integral Nonlinearity Error vs. DAC Code, +5 V Span
Figure 10. Differential Nonlinearity Error vs. DAC Code, +10 V Span
Rev. D | Page 9 of 28
AD5781
Data Sheet
0.5
0.3
0.2
T
T
T
= +125°C
= +25°C
= –40°C
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
A
A
A
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
0.4
V
= +5V
= 0V
REFP
REFN
V
V
= +15V
= –15V
DD
SS
V
0.3
0.2
0.1
0
0.1
0
–0.1
–0.2
–0.3
–0.4
–0.5
–0.1
–0.2
–0.3
–0.4
–0.5
±10V SPAN MAX DNL
+5V SPAN MAX DNL
+10V SPAN MIN DNL
+10V SPAN MAX DNL
±10V SPAN MIN DNL
+5V SPAN MIN DNL
V
DD
= +15V
= –15V
V
SS
0
50000
100000
150000
200000
250000
–55
–35
–15
5
25
45
65
85
105
125
DAC CODE
TEMPERATURE (°C)
Figure 11. Differential Nonlinearity Error vs. DAC Code, +5 V Span
Figure 14. Differential Nonlinearity Error vs. Temperature
0.5
0.14
T
T
T
= +25°C
= –40°C
= +125°C
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
A
A
A
0.4
0.3
0.12
0.10
0.08
0.06
0.04
0.02
0
V
V
V
V
= +10V
= 0V
= +15V
REFP
REFN
INL MAX
DD
SS
0.2
= –15V
T
= 25°C
0.1
A
V
V
= +10V
= –10V
REFP
REFN
0
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
–0.1
–0.2
–0.3
–0.4
–0.5
INL MIN
–0.02
–0.04
–0.06
0
50000
100000
150000
200000
250000
12.5
13.0
13.5
14.0
14.5
15.0
15.5
16.0
16.5
DAC CODE
V
/|V | (V)
DD SS
Figure 12. Differential Nonlinearity Error vs. DAC Code, 10 V Span,
X2 Gain Mode
Figure 15. Integral Nonlinearity Error vs. Supply Voltage, 10 V Span
0.5
0.4
AD8676 REFERENCE BUFFERS
0.4 AD8675 OUTPUT BUFFER
V
V
= +15V
= –15V
0.3
DD
SS
0.3
0.2
INL MAX
0.2
T
V
V
= 25°C
0.1
A
0.1
= +5V
REFP
REFN
= 0V
0
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
0
–0.1
–0.2
–0.1
–0.2
–0.3
–0.4
–0.5
±10V SPAN MAX INL
+5V SPAN MAX INL
+10V SPAN MIN INL
+10V SPAN MAX INL
±10V SPAN MIN INL
+5V SPAN MIN INL
INL MIN
–0.3
7.5
8.5
9.5
10.5 11.5 12.5 13.5 14.5 15.5 16.5
(V)
–55
–35
–15
5
25
45
65
85
105
125
V
DD
–2.5 –3.9 –5.3 –6.7 –9.1 –10.5 –12.9 –14.2 –15.5 –16.5
(V)
TEMPERATURE (°C)
V
SS
Figure 13. Integral Nonlinearity Error vs. Temperature
Figure 16. Integral Nonlinearity Error vs. Supply Voltage, +5 V Span
Rev. D | Page 10 of 28
Data Sheet
AD5781
0.08
0.14
0.12
T
V
V
= 25°C
A
0.06
= +5V
REFP
REFN
DNL MAX
= 0V
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
0.04
0.02
0.10
0.08
T
V
V
= 25°C
A
= +10V
REFP
REFN
0
= –10V
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
0.06
–0.02
0.04
0.02
–0.04
–0.06
DNL MIN
0
–0.08
7.5
8.5
9.5
10.5 11.5 12.5 13.5 14.5 15.5 16.5
(V)
12.5
13.0
13.5
14.0
14.5
15.0
15.5
16.0
16.5
V
DD
–2.5 –3.9 –5.3 –6.7 –9.1 –10.5 –12.9 –14.2 –15.5 –16.5
(V)
V
/|V | (V)
DD SS
V
SS
Figure 20. Zero-Scale Error vs. Supply Voltage, +5 V Span
Figure 17. Differential Nonlinearity Error vs. Supply Voltage, 10 V Span
0.05
0.04
0.10
0.05
T
V
V
= 25°C
A
= +10V
REFP
REFN
= –10V
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
DNL MAX
0.03
0.02
0.01
0
0
T
V
V
= 25°C
A
–0.05
–0.10
= +5V
REFP
REFN
= 0V
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
–0.15
–0.20
DNL MIN
–0.01
–0.02
–0.25
–0.03
7.5
8.5
9.5
10.5 11.5 12.5 13.5 14.5 15.5 16.5
(V)
12.5
13.0
13.5
14.0
14.5
15.0
15.5
16.0
16.5
V
DD
–2.5 –3.9 –5.3 –6.7 –9.1 –10.5 –12.9 –14.2 –15.5 –16.5
(V)
V
/|V | (V)
DD SS
V
SS
Figure 18. Differential Nonlinearity Error vs. Supply Voltage, +5 V Span
Figure 21. Midscale Error vs. Supply Voltage, 10 V Span
0.14
0.05
0.12
0.10
0.08
0.06
0
–0.05
–0.10
–0.15
–0.20
T
V
V
= 25°C
A
0.04
0.02
T = 25°C
A
= +10V
= –10V
REFP
REFN
V
V
= +5V
= 0V
REFP
REFN
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
0
12.5
7.5
8.5
9.5
10.5 11.5 12.5 13.5 14.5 15.5 16.5
(V)
13.0
13.5
14.0
14.5
15.0
15.5
16.0
16.5
V
DD
–2.5 –3.9 –5.3 –6.7 –9.1 –10.5 –12.9 –14.2 –15.5 –16.5
(V)
V
/|V | (V)
DD SS
V
SS
Figure 19. Zero-Scale Error vs. Supply Voltage, 10 V Span
Figure 22. Midscale Error vs. Supply Voltage, +5 V Span
Rev. D | Page 11 of 28
AD5781
Data Sheet
–0.015
0.10
0.05
0
T
= 25°C
A
V
V
= +5V
= 0V
REFP
REFN
–0.020
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
–0.05
–0.10
–0.15
–0.20
–0.25
–0.30
–0.35
–0.40
–0.025
–0.030
–0.035
–0.040
T
V
V
= 25°C
A
= +10V
REFP
REFN
= –10V
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
–0.045
12.5
13.0
13.5
14.0
14.5
15.0
15.5
16.0
16.5
7.5
8.5
9.5
10.5 11.5 12.5 13.5 14.5 15.5 16.5
V
(V)
V
/|V | (V)
DD
–2.5 –3.9 –5.3 –6.7 –9.1 –10.5 –12.9 –14.2 –15.5 –16.5
(V)
DD SS
V
SS
Figure 26. Gain Error vs. Supply Voltage, +5 V Span
Figure 23. Full-Scale Error vs. Supply Voltage, 10 V Span
0.15
0.10
0.07
0.06
0.05
INL MAX
0.05
0
0.04
0.03
0.02
0.01
T
V
V
= 25°C
A
= +15V
= –15V
DD
SS
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
–0.05
T
= 25°C
A
V
V
= +5V
= 0V
REFP
REFN
0
–0.01
–0.02
–0.10
–0.15
INL MIN
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
5.0
5.5
6.0
6.5
7.0
7.5
/|V
8.0
8.5
9.0
9.5 10.0
7.5
8.5
9.5
10.5 11.5 12.5 13.5 14.5 15.5 16.5
(V)
V
V
| (V)
DD
–2.5 –3.9 –5.3 –6.7 –9.1 –10.5 –12.9 –14.2 –15.5 –16.5
(V)
REFP
REFN
V
SS
Figure 24. Full-Scale Error vs. Supply Voltage, +5 V Span
Figure 27. Integral Nonlinearity Error vs. Reference Voltage
–0.30
–0.35
0.10
T
V
V
= 25°C
A
DNL MAX
= +10V
REFP
REFN
= –10V
0.05
0
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
–0.40
–0.45
T
V
V
= 25°C
A
= +15V
= –15V
DD
SS
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
–0.50
–0.55
–0.05
–0.10
–0.15
–0.60
–0.65
DNL MIN
12.5
13.0
13.5
14.0
14.5
15.0
15.5
16.0
16.5
5.0
5.5
6.0
6.5
7.0
7.5
/|V
8.0
8.5
9.0
9.5 10.0
V
/|V | (V)
V
| (V)
DD SS
REFP
REFN
Figure 25. Gain Error vs. Supply Voltage, 10 V Span
Figure 28. Differential Nonlinearity Error vs. Reference Voltage
Rev. D | Page 12 of 28
Data Sheet
AD5781
0.16
0.14
0.12
0.10
–0.30
–0.35
T
V
V
= 25°C
A
= +15V
= –15V
DD
SS
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
–0.40
–0.45
–0.50
–0.55
–0.60
T
V
V
= 25°C
A
0.08
0.06
0.04
= +15V
= –15V
DD
SS
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
0.02
0
5.0
5.5
6.0
6.5
7.0
7.5
/|V
8.0
8.5
9.0
9.5 10.0
5.0
5.5
6.0
6.5
7.0
7.5
/|V
8.0
8.5
9.0
9.5 10.0
V
| (V)
V
| (V)
REFP
REFN
REFP
REFN
Figure 29. Zero-Scale Error vs. Reference Voltage
Figure 32. Gain Error vs. Reference Voltage
0.3
0.2
0.1
0.03
0.02
0.01
0
±10V SPAN
+10V SPAN
±5V SPAN
0
–0.1
–0.01
–0.02
–0.03
–0.2
–0.3
–0.4
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
T
V
V
= 25°C
= +15V
A
DD
V
V
V
V
= +15V
= –15V
= –15V
DD
SS
SS
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
= +10V
= –15V
REFP
REFN
–0.04
–0.05
–0.5
–0.6
–55
–35
–15
5
25
45
65
85
105
125
5.0
5.5
6.0
6.5
7.0
7.5
/|V
8.0
8.5
9.0
9.5 10.0
TEMPERATURE (°C)
V
| (V)
REFP
REFN
Figure 30. Midscale Error vs. Reference Voltage
Figure 33. Full-Scale Error vs. Temperature
0.40
0.35
0.30
0.04
0.03
0.02
0.01
±10V SPAN
+10V SPAN
±5V SPAN
T
V
V
= 25°C
A
= +15V
= –15V
DD
SS
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
0.25
0.20
0.15
0.10
0.05
0
0
–0.01
–0.02
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
V
V
V
V
= +15V
= –15V
DD
SS
= +10V
= –15V
REFP
REFN
–0.03
–0.04
–55
–35
–15
5
25
45
65
85
105
125
5.0
5.5
6.0
6.5
7.0
7.5
/|V
8.0
8.5
9.0
9.5 10.0
TEMPERATURE (°C)
V
| (V)
REFP
REFN
Figure 34. Midscale Error vs. Temperature
Figure 31. Full-Scale Error vs. Reference Voltage
Rev. D | Page 13 of 28
AD5781
Data Sheet
1.2
1.0
0.8
0.6
5
4
±10V SPAN
+10V SPAN
±5V SPAN
T
= 25°C
A
I
DD
3
2
0.4
0.2
1
0
0
–1
–2
–3
–0.2
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
–0.4
V
V
V
V
= +15V
= –15V
DD
SS
–0.6
–0.8
–1.0
I
SS
= +10V
= –15V
REFP
REFN
–4
–5
–20
–15
–10
–5
0
5
10
15
20
–55
–35
–15
5
25
45
65
85
105
125
V
, V (V)
TEMPERATURE (°C)
DD SS
Figure 38. Power Supply Currents vs. Power Supply Voltages
Figure 35. Zero-Scale Error vs. Temperature
4
3
±10V SPAN
+10V SPAN
+5V SPAN
AD8676 REFERENCE BUFFERS
AD8675 OUTPUT BUFFER
V
V
V
V
= +15V
= –15V
DD
SS
2
1
= +10V
= –15V
REFP
REFN
V
V
V
V
= +15V
= –15V
DD
SS
= +10V
= –10V
0
REFP
REFN
3
AD8676 REFERENCE BUFFERS
OUTPUT UNBUFFERED
LOAD = 10MΩ||20pF
–1
–2
–3
–4
–5
4
CH3 5V
CH4 5V
200ns
–55
–35
–15
5
25
45
65
85
105
125
TEMPERATURE (°C)
Figure 36. Gain Error vs. Temperature
Figure 39. Rising Full-Scale Voltage Step
900
800
700
600
500
400
300
200
100
0
IOV = 5V, LOGIC VOLTAGE
CC
INCREASING
V
V
V
V
= +15V
= –15V
T
= 25°C
DD
SS
A
IOV = 5V, LOGIC VOLTAGE
CC
= +10V
= –10V
REFP
REFN
DECREASING
IOV = 3V, LOGIC VOLTAGE
CC
AD8676 REFERENCE BUFFERS
OUTPUT UNBUFFERED
LOAD = 10MΩ||20pF
INCREASING
IOV = 3V, LOGIC VOLTAGE
CC
DECREASING
3
4
CH3 5V
CH4 5V
200ns
0
1
2
3
4
5
6
LOGIC INPUT VOLTAGE (V)
Figure 37. IOICC vs. Logic Input Voltage
Figure 40. Falling Full-Scale Voltage Step
Rev. D | Page 14 of 28
Data Sheet
AD5781
10.8
10.6
10.4
10.2
10.0
9.8
3.0
2.6
2.2
±10V V
REF
OUTPUT GAIN OF 1
BIAS COMPENSATION MODE
20pF COMPENSATION CAPACITOR
RC LOW-PASS FILTER
5V V
REF
OUTPUT GAIN OF 1
BIAS COMPENSATION MODE
20pF COMPENSATION CAPACITOR
RC LOW-PASS FILTER
NEGATIVE CODE
CHANGE
POSITIVE CODE
CHANGE
1.8
1.4
1.0
0.6
9.6
0.2
9.4
0
–0.2
1
2
3
4
5
TIME (µs)
CODE
Figure 44. 6 MSB Segment Glitch Energy for 5 V VREF
Figure 41. 125 Code Step Settling Time
40
30
10
9
±10V V
REF
OUTPUT GAIN OF 1
BIAS COMPENSATION MODE
20pF COMPENSATION CAPACITOR
RC LOW-PASS FILTER
5V V
REF
OUTPUT GAIN OF 1
NEGATIVE CODE
CHANGE
BIAS COMPENSATION MODE
20pF COMPENSATION CAPACITOR
RC LOW-PASS FILTER
8
7
6
5
4
3
2
1
0
20
10
POSITIVE CODE
CHANGE
0
C
C
C
C
= 143pF + 0pF
X
X
X
X
–10
–20
= 143pF + 220pF
= 143pF + 470pF
= 143pF + 1,000pF
–1.0
–0.5
0
0.5
1.0
1.5
2.0
TIME (µs)
CODE
Figure 45. Midscale Peak-to-Peak Glitch for 10 V
Figure 42. 6 MSB Segment Glitch Energy for 10 V VREF
800
4.0
T
= 25°C
A
10V V
OUTPUT GAIN OF 1
BIAS COMPENSATION MODE
20pF COMPENSATION CAPACITOR
RC LOW-PASS FILTER
MID-SCALE CODE LOADED
OUTPUT UNBUFFERED
AD8676 REFERENCE BUFFERS
REF
V
V
V
V
= +15V
= –15V
DD
SS
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
600
400
= +10V
= –10V
REFP
REFN
POSITIVE CODE
CHANGE
NEGATIVE CODE
CHANGE
200
0
–200
–400
–600
0
1
2
3
4
5
6
7
8
9
10
TIME (Seconds)
CODE
Figure 46. Voltage Output Noise, 0.1 Hz to 10 Hz Bandwidth
Figure 43. 6 MSB Segment Glitch Energy for 10 V VREF
Rev. D | Page 15 of 28
AD5781
Data Sheet
100
V
V
V
V
= +15V
= –15V
DD
SS
= +10V
= –10V
REFP
REFN
CODE = MIDSCALE
10
1
0.1
1
10
100
1k
10k
100k
FREQUENCY (Hz)
Figure 47. Noise Spectral Density vs. Frequency
350
300
250
200
T
= 25°C
A
V
V
V
V
= +15V
= –15V
DD
SS
= +10V
= –10V
REFP
REFN
AD8675 OUTPUT BUFFER
150
100
50
0
–50
–1
0
1
2
3
4
5
6
TIME (µs)
Figure 48. Glitch Impulse on Removal of Output Clamp
Rev. D | Page 16 of 28
Data Sheet
AD5781
TERMINOLOGY
Relative Accuracy
Midscale Error Temperature Coefficient
Relative accuracy, or integral nonlinearity (INL), is a measure of
the maximum deviation, in LSB, from a straight line passing
through the endpoints of the DAC transfer function. A typical
INL error vs. code plot is shown in Figure 5.
Midscale error temperature coefficient is a measure of the
change in mid-scale error with a change in temperature. It is
expressed in ppm FSR/°C.
Output Slew Rate
Differential Nonlinearity (DNL)
Slew rate is a measure of the limitation in the rate of change of
the output voltage. The slew rate of the AD5781 output voltage
is determined by the capacitive load presented to the VOUT pin.
The capacitive load in conjunction with the 3.4 kΩ output
impedance of the AD5781 set the slew rate. Slew rate is
measured from 10% to 90% of the output voltage change and is
expressed in V/µs.
Differential nonlinearity is the difference between the measured
change and the ideal 1 LSB change between any two adjacent
codes. A specified differential nonlinearity of 1 LSB maximum
ensures monotonicity. This DAC is guaranteed monotonic. A
typical DNL error vs. code plot is shown in Figure 9.
Linearity Error Long-Term Stability
Linearity error long-term stability is a measure of the stability of
the linearity of the DAC over a long period of time. It is
specified in LSB for a time period of 500 hours and 1000 hours
at an elevated ambient temperature.
Output Voltage Settling Time
Output voltage settling time is the amount of time it takes for
the output voltage to settle to a specified level for a specified
change in voltage. For fast settling applications, a high speed
buffer amplifier is required to buffer the load from the 3.4 kΩ
output impedance of the AD5781, in which case, it is the
amplifier that determines the settling time.
Zero-Scale Error
Zero-scale error is a measure of the output error when zero-scale
code (0x00000) is loaded to the DAC register. Ideally, the output
voltage should be VREFNS. Zero-scale error is expressed in LSBs.
Digital-to-Analog Glitch Impulse
Digital-to-analog glitch impulse is the impulse injected into the
analog output when the input code in the DAC register changes
state. It is specified as the area of the glitch in nV-sec and is
measured when the digital input code is changed by 1 LSB at
the major carry transition (see Figure 42).
Zero-Scale Error Temperature Coefficient
Zero-scale error temperature coefficient is a measure of the
change in zero-scale error with a change in temperature. It is
expressed in ppm FSR/°C.
Full-Scale Error
Output Enabled Glitch Impulse
Full-scale error is a measure of the output error when full-scale
code (0x3FFFF) is loaded to the DAC register. Ideally, the
output voltage should be VREFPS − 1 LSB. Full-scale error is
expressed in LSBs.
Output enabled glitch impulse is the impulse injected into the
analog output when the clamp to ground on the DAC output is
removed. It is specified as the area of the glitch in nV-sec (see
Figure 48).
Full-Scale Error Temperature Coefficient
Full-scale error temperature coefficient is a measure of the
change in full-scale error with a change in temperature. It is
expressed in ppm FSR/°C.
Digital Feedthrough
Digital feedthrough is a measure of the impulse injected into
the analog output of the DAC from the digital inputs of the
DAC but is measured when the DAC output is not updated. It is
specified in nV-sec and measured with a full-scale code change
on the data bus, that is, from all 0s to all 1s, and vice versa.
Gain Error
Gain error is a measure of the span error of the DAC. It is the
deviation in slope of the DAC transfer characteristic from ideal,
expressed in ppm of the full-scale range.
Spurious Free Dynamic Range (SFDR)
Spurious free dynamic range is the usable dynamic range of a
DAC before spurious noise interferes or distorts the fundamental
signal. It is measured by the difference in amplitude between the
fundamental and the largest harmonically or nonharmonically
related spur from dc to full Nyquist bandwidth (half the DAC
sampling rate, or fS/2). SFDR is measured when the signal is a
digitally generated sine wave.
Gain Error Temperature Coefficient
Gain error temperature coefficient is a measure of the change in
gain error with a change in temperature. It is expressed in ppm
FSR/°C.
Midscale Error
Midscale error is a measure of the output error when midscale
code (0x20000) is loaded to the DAC register. Ideally, the output
voltage should be (VREFPS – VREFNS)/2 +VREFNS. Midscale error is
expressed in LSBs.
Total Harmonic Distortion (THD)
Total harmonic distortion is the ratio of the rms sum of the
harmonics of the DAC output to the fundamental value. Only
the second to fifth harmonics are included.
Rev. D | Page 17 of 28
AD5781
Data Sheet
DC Power Supply Rejection Ratio.
AC Power Supply Rejection Ratio (AC PSRR)
DC power supply rejection ratio is a measure of the rejection of
the output voltage to dc changes in the power supplies applied
to the DAC. It is measured for a given dc change in power
supply voltage and is expressed in µV/V.
AC power supply rejection ratio is a measure of the rejection of
the output voltage to ac changes in the power supplies applied
to the DAC. It is measured for a given amplitude and frequency
change in power supply voltage and is expressed in decibels.
Rev. D | Page 18 of 28
Data Sheet
AD5781
THEORY OF OPERATION
R
R
R
The AD5781 is a high accuracy, fast settling, single, 18-bit,
serial input, voltage output DAC. It operates from a VDD supply
voltage of 7.5 V to 16.5 V and a VSS supply of −16.5 V to −2.5 V.
Data is written to the AD5781 in a 24-bit word format via a 3-wire
serial interface. The AD5781 incorporates a power-on reset
circuit that ensures the DAC output powers up to 0 V with the
V
OUT
..........
.....................
2R
2R
E0
2R
2R
S0
2R
S1
2R
2R
..........
.....................
S11
E62
E61
V
REFPF
V
REFPS
V
REFNF
V
REFNS
12-BIT R-R LADDER
SIX MSBs DECODED INTO
63 EQUAL SEGMENTS
VOUT pin clamped to AGND through a ~6 kΩ internal resistor.
DAC ARCHITECTURE
Figure 49. DAC Ladder Structure Serial Interface
The architecture of the AD5781 consists of two matched DAC
sections. A simplified circuit diagram is shown in Figure 49.
The six MSBs of the 18-bit data-word are decoded to drive 63
switches, E0 to E62. Each of these switches connects one of 63
matched resistors to either the VREFP or VREFN voltage. The
remaining 12 bits of the data-word drive the S0 to S11 switches
of a 12-bit voltage mode R-R ladder network.
The AD5781 has a 3-wire serial interface (
, SCLK, and
SYNC
SDIN) that is compatible with SPI, QSPI, and MICROWIRE
interface standards, as well as most DSPs (see Figure 2 for a
timing diagram).
Input Shift Register
The input shift register is 24 bits wide. Data is loaded into the
device MSB first as a 24-bit word under the control of a serial
clock input, SCLK, which can operate at up to 35 MHz. The
W
input register consists of a R/ bit, three address bits, and
twenty data bits as shown in Table 7. The timing diagram for
this operation is shown in Figure 2.
Table 7. Input Shift Register Format
MSB
LSB
DB0
DB23
DB22
DB21
DB20
DB19
R/W
Register address
Register data
Table 8. Decoding the Input Shift Register
R/W
Register Address
Description
X1
0
0
0
0
1
1
1
0
0
0
0
1
0
0
0
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
No operation (NOP). Used in readback operations.
Write to the DAC register.
Write to the control register.
Write to the clearcode register.
Write to the software control register.
Read from the DAC register.
Read from the control register.
Read from the clearcode register.
1 X is don’t care.
Rev. D | Page 19 of 28
AD5781
Data Sheet
Standalone Operation
HARDWARE CONTROL PINS
The serial interface works with both a continuous and noncon-
tinuous serial clock. A continuous SCLK source can be used
LDAC
Load DAC Function (
)
After data has been transferred into the input register of the
DAC, there are two ways to update the DAC register and DAC
output. Depending on the status of both
of two update modes is selected: synchronous DAC updating or
asynchronous DAC updating.
SYNC
only if
In gated clock mode, a burst clock containing the exact number
SYNC
is held low for the correct number of clock cycles.
SYNC
LDAC
and , one
of clock cycles must be used, and
must be taken high
after the final clock to latch the data. The first falling edge of
SYNC
starts the write cycle. Exactly 24 falling clock edges must
Synchronous DAC Update
SYNC
be applied to SCLK before
SYNC
is brought high again. If
th
LDAC
In this mode,
the input shift register. The DAC output is updated on the rising
SYNC
is held low while data is being clocked into
is brought high before the 24 falling SCLK edge, the
data written is invalid. If more than 24 falling SCLK edges are
SYNC
edge of
Asynchronous DAC Update
LDAC
.
applied before
invalid. The input shift register is updated on the rising edge of
SYNC SYNC
is brought high, the input data is also
. For another serial transfer to take place,
must be
In this mode,
into the input shift register. The DAC output is asynchronously
LDAC SYNC
is held high while data is being clocked
brought low again. After the end of the serial data transfer, data
is automatically transferred from the input shift register to the
addressed register. Once the write cycle is complete, the output
updated by taking
The update now occurs on the falling edge of
RESET
low after
has been taken high.
LDAC
.
LDAC
SYNC
can be updated by taking
low while
is high.
Reset Function (
The AD5781 can be reset to its power-on state by two means:
RESET
)
Readback
The contents of all the on-chip registers can be read back via
the SDO pin. Table 8 outlines how the registers are decoded.
After a register has been addressed for a read, the next 24 clock
cycles clock the data out on the SDO pin. The clocks must be
either by asserting the
RESET control function (see Table 14). If the
used, it should be hardwired to IOVCC
Asynchronous Clear Function (CLR)
CLR
pin or by utilizing the software
RESET
pin is not
.
SYNC
SYNC
applied while
is low. When
is returned high, the
SDO pin is placed in tristate. For a read of a single register, the
NOP function can be used to clock out the data. Alternatively,
if more than one register is to be read, the data of the first
register to be addressed can be clocked out at the same time the
second register to be read is being addressed. The SDO pin
must be enabled to complete a readback operation. The SDO
pin is enabled by default.
The
pin is an active low clear that allows the output to be
cleared to a user defined value. The 18-bit clear code value is
programmed to the clearcode register (see Table 13). It is
CLR
necessary to maintain
to complete the operation (see Figure 2). When the
is returned high, the output remains at the clear value (if
low for a minimum amount of time
CLR
signal
LDAC
is high) until a new value is loaded to the DAC register. The
CLR
output cannot be updated with a new value while the
pin is
low. A clear operation can also be performed by setting the CLR
bit in the software control register (see Table 14).
Rev. D | Page 20 of 28
Data Sheet
AD5781
Table 9. Hardware Control Pins Truth Table
LDAC
CLR
X1
X1
0
1
0
1
0
1
0
RESET
Function
X1
X1
0
0
1
0
The AD5781 is in reset mode. The device cannot be programmed.
The AD5781 is returned to its power-on state. All registers are set to their default values.
The DAC register is loaded with the clearcode register value, and the output is set accordingly.
The output is set according to the DAC register value.
The DAC register is loaded with the clearcode register value, and the output is set accordingly.
The output is set according to the DAC register value.
The output remains at the clear code value.
The output remains set according to the DAC register value.
The output remains at the clear code value.
1
1
1
1
1
1
1
1
1
1
1
1
0
1
0
The DAC register is loaded with the clearcode register value and the output is set accordingly.
The DAC register is loaded with the clearcode register value and the output is set accordingly.
The output remains at the clear code value.
The output is set according to the DAC register value.
1 X is don’t care.
ON-CHIP REGISTERS
DAC Register
Table 10 outlines how data is written to and read from the DAC register.
Table 10. DAC Register
MSB
LSB
DB23
R/W
DB22
DB21
DB20
DB19
DB2
DAC register data
18-bits of data
DB1
DB0
Register address
0
0
1
X1
X1
R/W
1 X is don’t care.
The following equation describes the ideal transfer function of the DAC:
VREFP −VREFN ×D
(
)
VOUT
=
+VREFN
2
18 −1
where:
V
V
REFN is the negative voltage applied at the VREFNS input pin.
REFP is the positive voltage applied at the VREFPS input pin.
D is the 18-bit code programmed to the DAC.
Rev. D | Page 21 of 28
AD5781
Data Sheet
Control Register
The control register controls the mode of operation of the AD5781.
Table 11. Control Register
MSB
LSB
DB23 DB22 DB21 DB20 DB19...DB11
DB10
DB9 DB8 DB7 DB6 DB5
Control register data
Reserved LIN COMP SDODIS BIN/2sC DACTRI OPGND RBUF Reserved
DB4
DB3
DB2
DB1
DB0
R/W
R/W
Register address
0
1
0
Reserved
Table 12. Control Register Functions
Function
Reserved
RBUF
Description
These bits are reserved and should be programmed to zero.
Output amplifier configuration control.
0: internal amplifier, A1, is powered up and resistors RFB and R1 are connected in series as shown in Figure 52. This allows
an external amplifier to be connected in a gain of two configurations. See the AD5781 Features section for further details.
1: (default) internal amplifier, A1, is powered down and resistors RFB and R1 are connected in parallel as shown in Figure 51
so that the resistance between the RFB and INV pins is 3.4 kΩ, equal to the resistance of the DAC. This allows the RFB and INV
pins to be used for input bias current compensation for an external unity gain amplifier. See the AD5781 Features section
for further details.
OPGND
Output ground clamp control.
0: DAC output clamp to ground is removed, and the DAC is placed in normal mode.
1: (default) DAC output is clamped to ground through a ~6 kΩ resistance, and the DAC is placed in tristate mode.
Resetting the part puts the DAC in OPGND mode, where the output ground clamp is enabled and the DAC is tristated.
Setting the OPGND bit to 1 in the control register overrules any write to the DACTRI bit
DACTRI
DAC tristate control.
0: DAC is in normal operating mode.
1: (default) DAC is in tristate mode.
BIN/2sC
SDODIS
LIN COMP
DAC register coding select.
0: (default) DAC register uses twos complement coding.
1: DAC register uses offset binary coding.
SDO pin enable/disable control.
0: (default) SDO pin is enabled.
1: SDO pin is disabled (tristate).
Linearity error compensation for varying reference input spans. See the AD5781 Features section for further details.
0
1
0
1
0
0
0
0
(Default) reference input span up to 10 V.
Reference input span of 20 V.
Clearcode Register
The clearcode register sets the value to which the DAC output is set when the
pin or CLR bit is asserted. The output value depends
CLR
on the DAC coding that is being used, either binary or twos complement. The default register value is 0.
Table 13. Clearcode Register
MSB
LSB
DB23
R/W
DB22
DB21
DB20
DB19
DB2
Clearcode register data
18-bits of data
DB1
DB0
Register address
1
R/W
0
1
X1
X1
1 X is don’t care.
Rev. D | Page 22 of 28
Data Sheet
AD5781
Software Control Register
This is a write only register in which writing a 1 to a particular bit has the same effect as pulsing the corresponding pin low.
Table 14. Software Control Register
MSB
LSB
DB23
DB22
DB21
DB20
DB19
DB3
DB2
Software control register data
RESET
CLR1
DB1
DB0
LDAC2
W
Register address
0
R/
0
1
0
Reserved
1
LDAC
CLR
The CLR function has no effect if the
The LDAC function has no effect if the
pin is low.
pin is low.
2
Table 15. Software Control Register Functions
Function
Description
LDAC
Setting this bit to 1 updates the DAC register and consequently the DAC output.
CLR
Setting this bit to 1 sets the DAC register to a user defined value (see Table 13) and updates the DAC output. The output
value depends on the DAC register coding that is being used, either binary or twos complement.
RESET
Setting this bit to 1 returns the AD5781 to its power-on state.
Rev. D | Page 23 of 28
AD5781
Data Sheet
AD5781 FEATURES
Unity Gain Configuration
POWER-ON TO 0 V
Figure 50 shows an output amplifier configured for unity gain,
in this configuration the output spans from VREFN to VREFP.
The AD5781 contains a power-on reset circuit that, as well as
resetting all registers to their default values, controls the output
voltage during power-up. Upon power-on, the DAC is placed in
tristate (its reference inputs are disconnected), and its output is
clamped to AGND through a ~6 kΩ resistor. The DAC remains
in this state until programmed otherwise via the control
register. This is a useful feature in applications where it is
important to know the state of the DAC output while it is in the
process of powering up.
V
REFP
1/2 AD8676
V
REFPF
V
REFPS
A1
R
R1
R
FB
FB
AD8675,
6.8kΩ 6.8kΩ
ADA4898-1,
ADA4004-1
INV
OUT
CONFIGURING THE AD5781
18-BIT
DAC
V
V
OUT
After power-on, the AD5781 must be configured to put it into
normal operating mode before programming the output. To do
this, the control register must be programmed. The DAC is
removed from tristate by clearing the DACTRI bit, and the
output clamp is removed by clearing the OPGND bit. At this
point, the output goes to VREFN unless an alternative value is first
programmed to the DAC register.
AD5781
V
V
REFNS
REFNF
1/2 AD8676
V
REFN
Figure 50. Output Amplifier in Unity Gain Configuration
DAC OUTPUT STATE
A second unity gain configuration for the output amplifier is
one that removes an offset from the input bias currents of the
amplifier. It does this by inserting a resistance in the feedback
path of the amplifier that is equal to the output resistance of the
DAC. The DAC output resistance is 3.4 kΩ. By connecting R1
and RFB in parallel, a resistance equal to the DAC resistance is
available on-chip. Because the resistors are all on one piece of
silicon, they are temperature coefficient matched. To enable this
mode of operation, the RBUF bit of the control register must be set
to Logic 1. Figure 51 shows how the output amplifier is connected
to the AD5781. In this configuration, the output amplifier is in
unity gain and the output spans from VREFN to VREFP. This unity
gain configuration allows a capacitor to be placed in the
The DAC output can be placed in one of three states, controlled
by the DACTRI and OPGND bits of the control register, as
shown in Table 16.
Table 16. AD5781 Output State Truth Table
DACTRI OPGND Output State
0
0
1
1
0
1
0
1
Normal operating mode.
Output is clamped via ~6 kΩ to AGND.
Output is in tristate.
Output is clamped via ~6 kΩ to AGND.
LINEARITY COMPENSATION
The integral nonlinearity (INL) of the AD5781 can vary
according to the applied reference voltage span; the LIN COMP
bits of the control register can be programmed to compensate
for this variation in INL. The specifications in this data sheet
are obtained with LIN COMP = 0000 for reference spans up to
and including 10 V and with LIN COMP = 1100 for a reference
span of 20 V. The default value of the LIN COMP bits is 0000.
amplifier feedback path to improve dynamic performance.
V
REFP
1/2 AD8676
V
V
REFPS
REFPF
OUTPUT AMPLIFIER CONFIGURATION
R
FB
10pF
There are a number of different ways that an output amplifier
can be connected to the AD5781, depending on the voltage
references applied and the desired output voltage span.
R
R1 6.8kΩ
6.8kΩ
INV
FB
V
OUT
18-BIT
DAC
V
OUT
AD8675,
ADA4898-1,
ADA4004-1
AD5781
V
V
REFNS
REFNF
1/2 AD8676
V
REFN
Figure 51. Output Amplifier in Unity Gain with Amplifier Input Bias Current
Compensation
Rev. D | Page 24 of 28
Data Sheet
AD5781
V
REFP
Gain of Two Configuration
Figure 52 shows an output amplifier configured for a gain of
two. The gain is set by the internal matched 6.8 kΩ resistors,
which are exactly twice the DAC resistance, having the effect
of removing an offset from the input bias current of the external
1/2 AD8676
V
V
REFPF
REFPS
A1
R
R
R
1
FB
FB
amplifier. In this configuration, the output spans from 2 × VREFN
−
6.8kΩ 6.8kΩ
10pF
V
REFP to VR EFP. This configuration is used to generate a bipolar
INV
OUT
output span from a single-ended reference input, with VREFN
=
V
OUT
18-BIT
DAC
V
0 V. For this mode of operation, the RBUF bit of the control
register must be cleared to Logic 0.
AD8675,
ADA4898-1,
ADA4004-1
AD5781
V
V
REFNS
REFNF
1/2 AD8676
V
= 0V
REFN
Figure 52. Output Amplifier in Gain of Two Configuration
Rev. D | Page 25 of 28
AD5781
Data Sheet
APPLICATIONS INFORMATION
TYPICAL OPERATING CIRCUIT
Figure 53. Typical Operating Circuit
Figure 53 shows a typical operating circuit for the AD5781
using an AD8676 for reference buffers and an AD8675 as an
output buffer. To meet the specified linearity, force sense buffers
must be used on the reference inputs. Because the output
impedance of the AD5781 is 3.4 kΩ, an output buffer is
required for driving low resistive, high capacitive loads.
EVALUATION BOARD
An evaluation board is available for the AD5781 to aid
designers in evaluating the high performance of the part with
minimum effort. The AD5781 evaluation kit includes a
populated and tested AD5781 PCB. The evaluation board
interfaces to the USB port of a PC. Software is available with the
evaluation board to allow the user to easily program the
AD5781. The software runs on any PC that has Microsoft®
Windows® XP (SP2) or Vista (32 bits) installed. The EVAL-
AD5781 data sheet is available, which gives full details on the
operation of the evaluation board
Rev. D | Page 26 of 28
Data Sheet
AD5781
OUTLINE DIMENSIONS
6.60
6.50
6.40
20
11
10
4.50
4.40
4.30
6.40 BSC
1
PIN 1
0.65
BSC
1.20 MAX
0.15
0.05
0.20
0.09
0.75
0.60
0.45
8°
0°
0.30
0.19
COPLANARITY
0.10
SEATING
PLANE
COMPLIANT TO JEDEC STANDARDS MO-153-AC
Figure 54. 20-Lead Thin Shrink Small Outline Package [TSSOP]
(RU-20)
Dimensions shown in millimeters
ORDERING GUIDE
Model1
Temperature Range
INL
0.5 LSB
0.5 LSB
4 LSB
Package Description
20-Lead TSSOP
20-Lead TSSOP
20-Lead TSSOP
20-Lead TSSOP
Package Option
AD5781BRUZ
AD5781BRUZ-REEL7
AD5781ARUZ
AD5781ARUZ-REEL7
EVAL-AD5781SDZ
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
−40°C to +125°C
RU-20
RU-20
RU-20
RU-20
4 LSB
Evaluation Board
1 Z = RoHS Compliant Part.
Rev. D | Page 27 of 28
AD5781
NOTES
Data Sheet
©2010–2013 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D09092-0-7/13(D)
Rev. D | Page 28 of 28
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