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Circuit Note
CN-0047
Circuit Designs Using Analog Devices Products
Apply these product pairings quickly and with confidence.
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(1-800-262-5643) or visit www.analog.com/circuit.
Devices Connected/Referenced
AD7328
Bipolar Input, 8-Channel, 12-Bit
Plus Sign ADC
AD8620 Precision, Wide BS JFET Dual Op Amp
AD780 Ultrahigh Precision Voltage Reference
Using the AD7328 8-Channel ADC in Applications with Single-Ended Industrial-
Level Signals
Rev. A
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engineers. Standard engineering practices have been employed in the design and construction of
each circuit, and their function and performance have been tested and verified in a lab environment
at room temperature. However, you are solely responsible for testing the circuit and determining its
suitability and applicability for your use and application. Accordingly, in no event shall Analog
Devices be liable for direct, indirect, special, incidental, consequential or punitive damages due to
any cause whatsoever connected to the use of any “Circuit from the Lab”. (Continued on last page)
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Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2008-2010 Analog Devices, Inc. All rights reserved.
CIRCUIT FUNCTION AND BENEFITS
This circuit is designed to optimize the performance of the
AD7328 bipolar input, 8-channel, 12-bit plus sign ADC. The
AD7328 can operate at a throughput rate of 1 MSPS. The
selected operational amplifier (op amp) and reference voltage
source ensure that maximum AD7328 performance is achieved
with industrial-level, single-ended signal sources by providing a
low impedance driver with adequate settling time and an
accurate reference supply.
The AD7328 is designed on the iCMOS® (industrial CMOS)
process. This is a process combining high voltage silicon with
submicron CMOS and complementary bipolar technologies.
The AD7328 can accept true bipolar analog input signals. The
AD7328 has four software-selectable input ranges: ±10 V, ±5 V,
±2.5 V, and 0 V to +10 V. Each analog input channel can be
independently programmed to one of the four input ranges.
The analog input channels on the AD7328 can be programmed
to be single ended, true differential, or pseudo differential.
1µF
0.1µF
AD780
+2.5V
+12V
08535-001
V
IN
1.5kΩ
1.5kΩ
1.5kΩ
1.5kΩ
1.5kΩ
10kΩ
1.5kΩ
AD7328*
V
IN
+
V
DD
V
SS
V
CC
+12V+5V
*ADDITIONAL PINS OMITTED FOR CLARITY.
V
IN
–
AD8620
AD8620
REFIN
AGND
DGND
½
½
–12V
±10V
+12V
±10V
±
10V
V
DIFF
–12V
Figure 1. Single-Ended-to-Differential Input
(Simplified Schematic: Decoupling and All Connections Not Shown)
