CN0201: Complete 5 V, Single-Supply, 8-Channel Multiplexed Data Acquisition...

Circuit Note
CN-0201
Devices Connected/Referenced
Circuits from the Lab™ reference circuits are engineered and
tested for quick and easy system integration to help solve today’s
analog, mixed-signal, and RF design challenges. For more
information and/or support, visit www.analog.com/CN0201.
ADAS3022
16-Bit, 1 MSPS, 8 Channel Data Acquisition
System Acquisition System
ADP1613
650 kHz/1.3 MHz Step-Up PWM DC-to-DC
Switching Converter
AD8031/
AD8032
2.7 V, 800 μA per Amp, 80 MHz, Single/Dual,
Rail-to-Rail I/O Amplifiers
ADR434
Ultralow Noise XFET Voltage References
with Current Sink and Source Capability
Complete 5 V, Single-Supply, 8-Channel Multiplexed Data Acquisition System
with PGIA for Industrial Signal Levels
EVALUATION AND DESIGN SUPPORT
CIRCUIT FUNCTION AND BENEFITS
Circuit Evaluation Boards
ADAS Circuit Evaluation Board (EVAL-ADAS3022EDZ)
ADP1613 Evaluation Board Not Included
Converter Evaluation and Development Board (EVAL-CED1Z)
Design and Integration Files
Schematics, Layout Files, Bill of Materials
The circuit shown in Figure 1 is a highly integrated 16-bit, 1 MSPS,
multiplexed 8-channel flexible data acquisition system (DAS) with
a programmable gain instrumentation amplifier (PGIA) capable
of handling the full range of industrial signal levels.
D2
+ COUT3
4.7µF
L2
47µH
C2
1µF
+
1.78Ω
RFILT
L1
47µH
+5V
VIN = +5V
+
D1
CIN +
1µF
L3
1µF
+15V
COUT1 + COUT2 +
1µF
2.2µF
VDDH
AVDD DVDD
VIO
RESET
PD
REN
50kΩ
ADP1613
COMP
+
CC2
10pF
R C1
100kΩ
IN0
IN1
IN2
IN2/IN3
IN3
IN4
IN4/IN5
IN5
IN6
IN6/IN7
IN7
FB
FREQ
EN
VIN
GND
SW
ADAS3022
SCK
MUX
PGIA
TEMP
SENSOR
DIN
REFIN
BUF
REF
VSSH
AGND DGND
–15V
RF1B
47.5kΩ
PulSAR
ADC
SDO
AUX–
Z1
DNI
BUSY
CS
COM
AUX+
CSS +
1µF
CNV
LOGIC/
INTERFACE
IN0/IN1
SS
CV5 + RS2
DNI
1µF
RF2
4.22kΩ
DIFF DIFF
PAIR COM
R S1
0Ω
REFx
+5V
+5V
4.096V
+
–
AD8031
ADR434
09729-001
ENABLE
C C1 +
12nF
C1
1µF
RB0
1Ω
Figure 1. Complete 5 V, Single-Supply, 8-Channel Data Acquisition Solution with Integrated PGIA
(Simplified Schematic: All Connections and Decoupling Not Shown)
Rev. B
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CN-0201
Circuit Note
A single +5 V supply powers the circuit, and a high efficiency,
low ripple boost converter generates the ±15 V that allows
processing differential input signals up to ±24.576 V with
±2 LSB INL (maximum), and ±0.5 LSB DNL (typical). For
high accuracy applications, this compact and cost-effective
circuit offers high precision, as well as low noise.
The successive approximation register (SAR)-based data
acquisition system includes true high impedance differential
input buffers; therefore, there is no need for additional buffering,
as is usually required to reduce kickback in capacitive digital-toanalog converter (DAC)-based SAR analog-to-digital converters
(ADCs). In addition, the circuit has high common-mode rejection,
eliminating the need for external instrumentation amplifiers, which
are typically required in applications where common-mode signals
are present.
The ADAS3022 is a complete 16-bit, 1 MSPS data acquisition
system that integrates an 8-channel, low leakage multiplexer; a
programmable gain instrumentation amplifier stage with a high
common-mode rejection; a precision low drift 4.096 V reference; a
reference buffer; and a high performance, no latency, 16-bit SAR
ADC. The ADAS3022 reduces its power at the end of each
conversion cycle; therefore, the operating currents and power
scale linearly with throughput make it ideal for the low sampling
rates in battery-powered applications.
The ADAS3022 has eight inputs and a COM input that can be
configured as eight single-ended channels, eight channels with
a common reference, four differential channels, or various
combinations of single-ended and differential channels.
In the circuit shown in Figure 1, the reference is supplied by the
ADR434 low noise reference buffered by an AD8031 op amp.
The AD8031 is ideally suited as a reference buffer because of its
ability to drive dynamic loads with fast recovery.
The ADP1613 is a dc-to-dc boost converter with an integrated
power switch and provides the ADAS3022 high voltage ±15 V
supplies required for the on-chip input multiplexer and the
programmable gain instrumentation amplifier without
compromising the performance of the ADAS3022.
performance at higher data rates, a smaller form factor, faster
time to market, and lower costs.
The ADAS3022 has an internal PGIA that can be set for gains
of 0.16, 0.2, 0.4, 0.8, 1.6, 3.2, and 6.4, and it can handle fully
differential input ranges of ±24.576 V, ±20.48 V, ±10.24 V,
±5.12 V, ±2.56 V, ±1.28 V, and ±0.64 V, respectively. The input
ranges are referenced to an internal 4.096 V reference voltage.
Pseudo-differential, unipolar, and bipolar input ranges are also
allowed where the input voltage is measured with respect to the
voltage on the COM pin.
In the circuit shown in Figure 1, the 4.096 V ADR434 provides the
external reference voltage. The ADR434 features high accuracy,
low power (800 µA operating current), low noise, ±0.12% maximum
initial error, and excellent temperature stability. The low power
AD8032 op amp is used to buffer the external reference, making it
ideal for a wide range of applications from battery-operated systems
with large bandwidth requirements to high speed systems where
component density requires lower power dissipation.
The ADAS3022 digital interface consists of asynchronous inputs
(CNV, RESET, PD, and BUSY) and a 4-wire serial interface (CS,
SDO, SCK, and DIN) compatible with SPI, FPGA, or DSP for
conversion result readback and configuration register programming.
ADP1613 Power Design
The ADP1613 is used as the single-ended, primary inductance
(SEPIC) Cuk converter, which is an ideal candidate for providing
the ADAS3022 with the necessary high voltage ±15 V supplies
(at 20 mA) and low output ripple (3 mV maximum) from an
external 5 V supply. The switching frequency of the ADP1613
in this application is 1.3 MHz. The ADP1613 satisfies the
specification requirements of the ADAS3022 with a minimum
of external components, and the efficiency is greater than 86%,
as shown in Figure 2. The main advantage of using the low cost
ADP1613 in this topology is its excellent tracking between the
two supply rails, while creating the ±15 V using off-the-shelf
coupled inductors. In addition, it can be quickly and easily
designed and built using the ADIsimPower design tool.
This circuit offers high precision, as well as low noise, which is
ensured by the combination of the ADAS3022, ADP1613,
ADR434, and AD8031 precision components.
1.0
0.9
Rev. B | Page 2 of 5
VIN MIN
0.5
VIN MAX
0.4
0.3
0.2
0.1
0.020
IOUT (A)
Figure 2. ADP1613 Efficiency (POUT/PIN) vs. Output Current (IOUT)
09729-002
0.018
0.016
0.014
0.012
0.010
0.008
0.006
0
0.004
The ADAS3022 simplifies the design challenges of building a
precision 16-bit, 1 MSPS DAS by eliminating the need for signal
buffering, level shifting, amplification, rejection of noise, and
other analog signal conditioning required in standard solutions.
In addition, the ADAS3022 offers optimized timing and noise
0.6
0.002
The ADAS3022 is the first complete DAS on a single chip that
is capable of converting up to 1 MSPS and can accept differential
analog input signals up to ±24.576 V. The ADAS3022 requires
high voltage bipolar supplies: ±15 V (VDDH and VSSH), +5 V
(AVDD and DVDD), and +1.8 V to +5 V (VIO).
0.7
0
CIRCUIT DESCRIPTION
EFFICIENCY (POUT ÷ PIN)
0.8
Circuit Note
CN-0201
The circuit shown in Figure 1 was designed using the following
inputs within the ADP161x SEPIC-Cuk Downloadable Design
Tool, which is available at ADIsimPower:
•
•
•
•
•
•
•
VINMIN = 4.75 V
VINMAX = 4.99 V
VOUT = 15 V
VRIPPLE = 0.02%
Ambient temperature = 55°C
Optimized for lowest cost
External filter option
COMMON VARIATIONS
Other external 4.096 V references can be used with the ADAS3022
such as the ADR444 and ADR4540. The AD8031 or AD8605 op
amps can be used as external reference buffers, if desired.
The ADAS3022 data sheet should be consulted for further
recommendations regarding the use of internal or external
references and reference buffers.
Note that the maximum voltage on the SW pin of the ADP1613
is equal to VIN + VOUT = 20 V, which is less than its absolute
maximum voltage specification of 21 V. For input voltages greater
than or equal to 5 V, the design tool suggests an additional cascode
N-channel MOSFET driven by the SW pin. Because of the 1 V
safety margin, this FET is not required in the circuit for input
voltages up to 5.25 V with a 15 V output. Therefore, the input
voltage used in the design tool was set to 4.99 V. The design results
for the ADP1613 SEPIC-Cuk converter are located in the
CN0201-Design Support package.
Dynamic Performance
CIRCUIT EVALUATION AND TEST
This circuit was tested using an Analog Devices ADP1613
evaluation board, the EVAL-ADAS3022EDZ evaluation board,
and the EVAL-CED1Z converter evaluation and development
board connected as shown in Figure 4. The 7 V wall wart was
connected to the EVAL-CED1Z, and the external 5 V supply
was connected to the ADP1613 evaluation board.
The EVAL-ADAS3022EDZ is a customer evaluation board
intended to ease standalone testing of performance and
functionality for the 16-bit ADAS3022 complete DAS. The
ADP1613 evaluation board was built using the ADP161x
SEPIC-Cuk Downloadable Design Tool available at ADIsimPower.
09729-003
Figure 3 shows the typical dynamic performance of the ADAS3022
with an ac input signal. Experiments were conducted with the
ADAS3022 driven from linear ±15 V bench supplies and driven
from the ±15 V output of the ADP1613 evaluation board. No
difference in ac or dc performance was observed.
The ADP1612/ADP1613/ADP1614 are step-up, dc-to-dc
converters with an integrated power switch that is capable of
providing an output voltage up to 20 V. When used as a SEPICCuk converter, the current output capability of the ADP1613
is up to 60 mA. The ADP1614 supplies up to 120 mA. The
ADIsimPower design tool allows complete customization of
the design and to quickly create the robust dual rails from one
controller using an inexpensive SEPIC-Cuk topology.
Figure 3. FFT Output of the ADAS3022 Using the EVAL-CED1Z Evaluation Board and Software
Rev. B | Page 3 of 5
CN-0201
Circuit Note
Software Installation
The EVAL-CED1Z board is a platform intended for use in
evaluation, demonstration, and development of systems using
Analog Devices precision converters. It provides the necessary
communications between the converter and the PC, programming
or controlling the device, and transmitting or receiving data
over a USB link.
The ADAS3022 evaluation kit includes self-installing software
on a CD. The software is compatible with Windows XP and
Windows 7 (32-bit and 64-bit). If the setup file does not run
automatically, run the setup.exe file from the CD.
To install the software, take the following steps:
Equipment Required
1.
The following equipment is required:
•
•
•
•
•
•
•
The ADAS circuit evaluation board and software (EVALADAS3022EDZ)
The converter evaluation and development board (EVALCED1Z)
The ADP1613 evaluation board from ADIsimPower
Audio Precision SYS-2702
PC/laptop (Windows 32-bit or 64-bit)
USB interface Cable (1) and AP cable (1)
7 V at 2 A dc wall wart supply for EVAL-CED1Z board.
5 V at 100 mA dc power supply for ADP1613 evaluation
board.
2.
3.
The software allows the collection and processing of FFT data as
previously shown in Figure 3. Refer to the UG-484 User Guide for
complete information on the EVAL-ADAS3022EDZ test setup.
Functional Block Diagram
For more details on the definitions and how to calculate the signalto-noise ratio (SNR), total harmonic distortion (THD), and
signal-to-(noise + distortion) ratio (SINAD), see the Terminology
section of the ADAS3022 data sheet and the Data Conversion
Handbook, "Testing Data Converters," Chapter 5, Analog Devices.
A functional block diagram of the test setup is shown in Figure 4.
The ADP1613 evaluation board is driven with an external +5 V
supply to generate the ±15 V required by the ADAS3022 board.
A 7 V dc wall wart supplies the EVAL-CED1Z board. The 5 V
required by the ADAS3022 board is supplied by regulators on
the EVAL-CED1Z board. An Audio Precision SYS-2702 is used
to generate a low distortion input signal when running ac tests.
AGILENT
E3630A
+5V
ADP1613
+15V
POWER
SUPPLY
WALL
WART
+7V AT 2A
–15V
EVAL-ADAS3022EDZ
DECIMATED
DATA
AIN0 TO AIN7
ADAS3022
ADR434
FPGA
CONTROL
SIGNALS
CONVERTER
EVALUATION AND
DEVLOPMENT BOARD
(EVAL-CED1Z)
+5V
Figure 4. Test Setup Functional Block Diagram
Rev. B | Page 4 of 5
USB
CABLE
PC
DATA
ANAYLYSIS
SOFTWARE
09729-004
•
Install the evaluation software before connecting the
ADAS3022 evaluation board and EVAL-CED1Z board to
the USB port of the PC to ensure that the evaluation
system is correctly recognized when connected to the PC.
After installation from the CD is complete, connect the
EVAL-CED1Z board to the ADAS3022 evaluation board
and power up the EVAL-CED1Z as described in the Power
Supplies section of UG-484 and then to the USB port of the
PC using the supplied cable.
When the evaluation system is detected, proceed through any
dialog boxes that appear. This completes the installation.
Circuit Note
CN-0201
LEARN MORE
Data Sheets and Evaluation Boards
CN-0201 Design Support Package:
www.analog.com/CN0201-DesignSupport.
ADAS3022 Data Sheet and Evaluation Board
AN-1106 Application Note, An Improved Topology for Creating
Split Rails from a Single Input Voltage.
ADR434 Data Sheet
CN-0105 Circuit Note, Single-Ended-to-Differential High Speed
Drive Circuit for 16-Bit, 10 MSPS AD7626 ADC.
REVISION HISTORY
CN-0237 Circuit Note, Ultralow Power, 18-Bit, Differential
PulSAR ADC Driver.
ADP1613 Data Sheet
AD8031 Data Sheet
8/13—Rev. A to Rev. B
Changes to Figure 1 .......................................................................... 1
Kester, Walt. 2005. The Data Conversion Handbook. Analog
Devices. Chapter 3, Chapter 5, and Chapter 7.
4/13—Rev. 0 to Rev. A
Changes to Figure 1 .......................................................................... 1
MT-021 Tutorial, ADC Architectures II: Successive
Approximation ADCs. Analog Devices.
10/12—Revision 0: Initial Version
MT-031 Tutorial, Grounding Data Converters and Solving the
Mystery of AGND and DGND. Analog Devices.
MT-035 Tutorial, Op Amp Inputs, Outputs, Single-Supply, and
Rail-to-Rail Issues. Analog Devices.
MT-101 Tutorial, Decoupling Techniques. Analog Devices.
User Guide UG-484 for EVAL-ADAS3022EDZ.
Voltage Reference Wizard Design Tool.
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CN09729-0-8/13(B)
Rev. B | Page 5 of 5
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