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Circuits from the Lab Reference Designs
Precision Data Acquisition
About Circuits from the Lab Reference Designs
ADI Circuits from the Lab® Reference Designs are built and tested for
function and performance by ADI’s applications experts. Circuits from the Lab
support quick and easy evaluation, prototyping, and design integration, and offer:
• Comprehensive documentation
• Complete design and integration files
• Factory tested evaluation hardware
Precision Data Acquisition Circuits from the Lab Reference Designs are
application agnostic and are commonly used in analog signal chain design as
standalone solutions, or to build more complex circuits and subsystems.
Precision Data Acquisition
Application Introduction
Precision data acquisition systems (DAQs) are essential to many
medical, industrial, instrumentation, and military applications. Resolution
requirements range from 16 bits to 24 bits, and sampling rates from a few
Hz to several MHz. In multichannel systems, analog multiplexers allow a
single analog-to-digital converter (ADC) to sample a number of channels,
thereby lowering cost and printed circuit board real estate. Choosing
the proper ADC is an important design consideration, as well as the
supporting circuitry, including the voltage reference, input drive amplifier,
instrumentation amplifier, multiplexer, and power supply.
Design Considerations and Major Challenges
Successive approximation (SAR) and sigma-delta (Σ-Δ) are the most
popular ADC architectures for data acquisition systems. However, choosing
the correct architecture for an application can be a challenging task.
Successive approximation ADCs are available with resolutions of up to
18 bits and sampling rates of several MSPS (see CN0277 that highlights the
AD7960 18-bit, 5 MSPS ADC). They are ideal for multiplexed applications
requiring a large number of channels (see CN0254 and CN0269). SAR ADCs find widespread applications in
medical imaging, electronic test and measurement, and industrial applications such as programmable logic
controllers (PLCs) and distributed control systems (DCSs).
Σ-Δ ADCs have resolutions up to 24 bits and are ideal for precision measurement applications that use low
sampling rates (see CN0251 and CN0310). High resolution allows a direct interface to many sensors such as
thermocouples, load cells, and RTDs. Some Σ-Δ ADCs have internal programmable gain amplifiers that facilitate
processing low level signals without the requirement for additional gain components.
The design of a DAQ can be quite challenging because of the many trade-offs possible. For example, industrial
signals of ±10 V require special conditioning to interface with single-supply differential input ADCs (see CN0251,
CN0269, and CN0310). Harsh industrial environments may also require high voltage digital isolators to protect
sensitive circuits (see CN0254). Making the proper trade-offs between power dissipation, dynamic performance,
PCB area, and cost is important for a competitive design, and achieving required performance depends on careful
attention to layout, grounding, and decoupling techniques.
www.analog.com/circuits-from-the-lab
Circuits from the Lab Reference Designs­—Precision Data Acquisition
Circuits from
the Lab
Reference
Designs
CN0310
Resolution
(Bits)
Sampling
Rate
(kSPS)
Number
of
Channels
Converter
Architecture
Input
Signal Range
(V)
Power
Dissipation
(mW)
Data
Output
Format
24
250
1
Σ-Δ
±10, ±5,
0 to +10
54
Evaluation Hardware
Pricing
($/ea)
SPI
EVAL-AD7176-2SDZ*
59.00
130
SPI
EVAL-CN0251-SDPZ*
80.00
EVAL-AD7960FMCZ**
99.00
EVAL-CN0269-SDPZ*
100.00
EVAL-CN0261-SDPZ*
79.00
EVAL-CN0305-SDPZ*
99.00
CN0251
24
4.7 Hz
4
Σ-Δ
±10, ±5,
±1, ±500 mV,
±250 mV,
±125 mV, ±62,
5 mV, ±31.25
mV
CN0277
18
5 MSPS
1
PulSAR®
0 to +5
122
LVDS
CN0269
18
1.33 MSPS
16
PulSAR
±10, ±5
337
SPI
CN0261
18
250
1
PulSAR
0 to +5
107
SPI
CN0305
16
300
1
PulSAR
0 to +5
11
SPI
CN0254
16
250
8
PulSAR
±10
294
SPI
CN0306
16
100
1
PulSAR
0 to +5
7.4
SPI
CN0255
16
100
1
PulSAR
Additional
Features
8
0 to +2.5
SPI
Optimized
for ac
performance
Optimized
for ac
performance
Optimized for
sub-Nyquist
input signals
up to 4 kHz
Isolated
Optimized for
sub-Nyquist
input signals
up to 4 kHz
EVAL-CN0254-SDPZ*
75.00
EVAL-CN0306-SDPZ*
99.00
EVAL-CN0255-SDPZ*
79.00
* This reference design also requires EVAL-SDP-CB1Z ($99.00)
** This reference design also requires EVAL-SDP-CH1Z ($199.00)
Highlighted Circuits from the Lab Reference Designs
+7V
+5V
SINGLE ENDED
+5V
+12V
VDD
AI0
AI1
AI2
AI3
AI4
AI5
AI6
AI7
S1
S2
S3
S4
S5
S6
S7
S8
AI0+
AI1+
AI2+
AI3+
AI4+
AI5+
AI6+
AI7+
–12V
VSS
GND
P4
AGND
+12V
EN
A0
A1
A2
ADG5208
–12V
VDD
GND
S1A
S1B
S2A
S2B
NC_1
NC_2
NC_3
+12V
VDD
AI8
AI9
AI10
AI11
AI12
AI13
AI14
AI15
S1
S2
S3
S4
S5
S6
S7
S8
AI0–
AI1–
AI2–
AI3–
AI4–
AI5–
AI6–
AI7–
–12V
DIFFERENTIAL
VSS
GND
D
NC_4
NC_5
ADG5236
1.25kΩ
2 –IN_0.4*
–12V
+12V
–12V
1kΩ
0.1µF
1.25kΩ
3 –IN_0.8*
VCOM
3
+IN_0.8*
2
+IN_0.4*
1
JP4
+VS
1.25kΩ
1.25kΩ
NC
1kΩ
+OUT
–OUT
VIO
10kΩ
10Ω
2.2nF
IN+
2.2nF
REF VDD
IN–
10Ω
GND
AD8475
ADG5208
33Ω
33Ω
33Ω
Y
B
A
CN0269:18-bit, 1.33 MSPS, 16-channel data acquisition system.
| Circuits from the Lab Reference Designs
2
74LVC1G00
VCM = VREF ÷ 2
= 2.5V
VIO
SDI
SCK
SDO
CNV
33Ω
33Ω
33Ω
TCLKBF
DATA
TFS
VREF = 5V
CP
15Ω
0.1µF
PL
U/D
P0
P1
P2
P3
P0
P1
P2
P3
S_D
EN
IN+
CNV+/
CNV–
100Ω
VCM = VREF ÷ 2
= 2.5V
VIN–
0.1µF
820Ω
GND
56pF
ADA4897-1 0.1µF
DCO+/DCO–
IN–
33Ω
100pF
1kΩ
100Ω
D+/D–
AD7960
+VS +7V/+5V/EXT
0.1µF
74LVC169
REFIN REF VDD1 VDD2 VIO
ADA4897-1 0.1µF
–2.5V/EXT –VS
VIN–
GPIO
PE
U/D
56pF
VIN+
GND
Q0
Q1
Q2
Q3
33Ω
1kΩ
VCM = 2.5V
AD7984
VCC
GND
CEP
CET
TC
+5V
+1.8V
820Ω
100pF
+3.3V
33Ω
33Ω
33Ω
VIN+
SPORT
–VS
AD8065
CH0 CH1 CH2 CH3
EN
A0
A1
A2
+VS +7V/+5V/EXT
0.1µF
0Ω
VCOM
JP3
1
1kΩ
1kΩ
0.1µF
50V
22µF
6.3V
+5V
+12V
IN2
0.1µF
50V
ADR4550
+2.5V
+4.096V
TP_2
NC_2
VOUT
TRIM
ADR444
1kΩ
IN1
D2
DGND
AD8065
VSS
D1
TP_1
VIN
NC_1
GND
0.1µF
50V
D
+7V
+5V
AD8031
VCM
CLK+/CLK–
100Ω
100Ω
+2.5V
+7V
AD8031
–2.5V/EXT –VS
CN0277: high precision, 18-bit, 5 MSPS, low power data acquisition signal chain.
Key Products
Analog-to-Digital Converters
Resolution (Bits)
Throughput Rate Max (kSPS)
Architecture
Full Power BW (MHz)
Number of
Channels
Package
AD7176-2
24
250
4
TSSOP
24
18
18
18
16
16
16
4.8
5 MSPS
250
1.33 MSPS
250
500
100
Σ-Δ
Σ-Δ
N/A­
AD7192
AD7960
AD7691
AD7984
AD7689
AD7988-5
AD7988-1
­N/A­
28
2
10
1.7
10
10
4
1
1
1
8
1
1
TSSOP
LFCSP
MSOP, LFCSP
MSOP, LFCSP
LFCSP
MSOP, LFCSP
MSOP, LFCSP
Part Number
PulSAR
PulSAR
PulSAR
PulSAR
PulSAR
PulSAR
Rail-to-Rail Output Fully Differential Funnel Amplifier
Part Number
∙3 dB BW
(MHz)
Slew Rate
(V/s)
Closed-Loop
Gain
Input Offset
Voltage (V)
Min Pos
Supply (V)
Max Pos
Supply (V)
Supply Current
per Amplifier
(mA)
Amplifiers per
Package
Package
150
50
0.4, 0.8
200
3
10
3
1
MSOP, LFCSP
AD8475
Rail-to-Rail Output Instrumentation Amplifier
Part Number
Gain (Min)
Gain (Max)
Min CMRR @
60 Hz, G = 1 (dB)
VSUPPLY Span
Min (V)
VSUPPLY Span
Max (V)
Supply Current
(A)
Voltage Noise RTI
(V p-p)
Package
1
1000
86
2.2
36
400
2
MSOP, SOIC
AD8226
Operational Amplifiers
Small Signal
Bandwidth
(MHz)
Slew Rate
(V/s)
Input Offset
Voltage (V)
Amplifiers per
Package
VSUPPLY Span
Min (V)
AD8031
80
35
1 mV
1
2.7
12
Input, output
0.9
AD8032
80
35
1 mV
2
2.7
12
Input, output
0.9
ADA4897-1
ADA4897-2
230
230
120
120
28
28
1
2
3
3
10
10
Output
Output
3
3
AD8065
145
180
400
1
5
24
Output
6.4
Part Number
VSUPPLY Span
Rail-Rail
Supply Current
Max (V)
Input/Output per Amplifier (mA)
Package
PDIP, SOIC,
SOT-23
PDIP, SOIC,
MSOP
SOIC, SOT-23
MSOP
MSOP, SOIC,
SOT-23
AD8597
10
14
10
1
10
36
­
4.8
SOIC, LFCSP
OP1177
AD8605
AD8608
AD8609
AD8641
1.3
10
10
400 kHz
3.5
0.7
5
5
0.1
3
15
20
20
12
50
1
1
4
4
1
5
2.7
2.7
1.8
5
36
6
6
5
26
­
Input, output
Input, output
Input, output
Output
0.4
1
1
0.05
0.25
MSOP, SOIC
SOT-23, WLCSP
SOIC, TSSOP
SOIC, TSSOP
SC70, SOIC
80
13
40
1
2.7
12
Output
1.1
SOT-23, SOIC
ADA4841-1
Voltage References
Part Number
ADR445
ADR444
ADR4550
ADR435
ADR4525
VOUT (V)
5
4.096
5
5
2.5
Initial Accuracy
(%)
0.04
0.04
0.02
0.04
0.02
Ref Out TC
(ppm/∙C)
1
1
2
1
2
0.1 Hz to 10 Hz
Noise (V p-p)
2.25
1.8
2.8
8
1.25
Reference Type
Max Input Voltage (V)
Series low dropout
Series low dropout
Series low dropout
Series
Series low dropout
18
18
15
18
15
Dropout Voltage
(mV)
500
500
300
2V
300
Package
MSOP, SOIC
MSOP, SOIC
SOIC
MSOP, SOIC
SOIC
isoPower Digital Isolators
Part Number
ADuM3471
Number of
Inputs Side 1
Number of
Inputs Side 2
3
1
Insulation
Rating
(kV rms)
2.5
Max Data Rate
(Mbps)
Prop Delay
(ns)
Isolated Output
Supply (mA)
Isolated Output
Voltage Min/
Max (V)
Max Pos
Supply (V)
Package
25
60
400
3.3/24
5.5
SSOP
www.analog.com/circuits-from-the-lab | 3
Linear Regulators
Part Number
ADP1720
ADP3336
VIN Min (V)
VIN Max (V)
VOUT Preset
Max VOUT Adj
(V)
Min VOUT Adj
(V)
IOUT (Max)
(mA)
4
2.6
28
12
3.3, 5.0
N/A
5
10
1.225
1.5
50
500
Dropout Voltage
@ Rated IOUT (mV)
275
200
Package
MSOP
MSOP
Analog Multiplexers
Part Number
Sw/Mx Function
∙ Number
ADG5208
(8:1) × 1
Max Analog
Signal Range
–3 dB Bandwidth
(MHz)
Supply V Guar
Performance (V)
RON (Ω)
Transistion Time
(ns)
Package
54
Dual: (±15),
Dual: (±20),
Single: (+12),
Single: (+36)
160
170
TSSOP, LFCSP
160
150
TSSOP, LFCSP
4
140
TSSOP, LFCSP
VSS to VDD
ADG5236
(2:1) × 2
VSS to VDD
266
Dual: (±15),
Dual: (±20),
Single: (+12),
Single: (+36)
ADG1409
(4:1) × 2
VSS to VDD
115
Dual: (±15),
Dual: (±5),
Single: (+12)
Additional Design Resources
Technical Books and Articles
Data Conversion Handbook—www.analog.com/library/analogdialogue/archives/39-06/data_conversion_handbook.html
• ADC Architectures (Chapter 3.2)
• Interfacing to Data Converters (Chapter 6)
• Multichannel Data Acquisition Systems (Chapter 8.2)
Which ADC Architecture Is Right for Your Application?, Analog Dialogue—
www.analog.com/library/analogdialogue/archives/39-06/architecture.html
A Practical Guide to High-Speed Printed-Circuit-Board Layout, Analog Dialogue—
www.analog.com/library/analogdialogue/archives/39-09/layout.html
Tutorials
• MT-021: Successive Approximation ADCs—www.analog.com/MT-021
• MT-022: ∑-∆ ADCs—www.analog.com/MT-022
• MT-031: Grounding Data Converters—www.analog.com/MT-031
• MT-101: Decoupling Techniques—www.analog.com/MT-101
Design Tools and Forums
• Signal Chain Designer™ Advanced Selection and Design Environment—www.analog.com/signalchaindesigner
• EngineerZone™ Online Technical Support Community—ez.analog.com
• ADIsimADC™ Converter Modeling Tool—www.analog.com/adisimadc
Customer Interaction Center
Email
North America: [email protected]
Europe: [email protected]
Asia: [email protected]
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