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Circuit Note
CN-0376
Circuits from the Lab® reference designs 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/CN0376.
Devices Connected/Referenced
AD7124-4
8-Channel, Low Noise, Low Power, 24-Bit,
Sigma-Delta ADC with PGA and Reference
ADuM5010 2.5 kV rms, Isolated DC-to-DC Converter
ADuM1441 Micropower Quad-Channel Digital Isolator
ADP2441
36 V, 1 A, Synchronous, Step-Down
DC-to-DC Regulator
Channel-to-Channel Isolated Temperature Input (Thermocouple/RTD) for
PLC/DCS Applications
Rev. 0
Circuits from the Lab reference designs from Analog Devices have been designed and built by Analog
Devices 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 Circuits from the Lab circuits. (Continued on last page)
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700 www.analog.com
Fax: 781.461.3113 ©2015 Analog Devices, Inc. All rights reserved.
EVALUATION AND DESIGN SUPPORT
Circuit Evaluation Boards
CN-0376 Circuit Evaluation Board (EVAL-CN0376-SDPZ)
System Demonstration Platform (EVAL-SDP-CB1Z)
Design and Integration Files
Schematics, Layout Files, Bill of Materials
CIRCUIT FUNCTION AND BENEFITS
The circuit shown in Figure 1 provides a dual-channel, channel-
to-channel isolated, thermocouple or RTD input suitable for
programmable logic controllers (PLC) and distributed control
systems (DCS). The highly integrated design utilizes a low
power, 24-bit, Σ-Δ analog-to-digital converter (ADC) with a
rich analog and digital feature set that requires no additional
signal conditioning ICs.
Each channel can accept either a thermocouple or a RTD input.
The entire circuit is powered from a standard 24 V bus supply.
Each channel measures only 27 mm × 50 mm.
Figure 1. PLC/DCS Channel-to-Channel Isolated Temperature Input (Simplified Schematic: All Connections and Decoupling Not Shown)
DUPLICATE CHANNEL
I
EXC
V
REF
AIN+
AIN–
1nF
3kΩ
3kΩ
5.62kΩ
1
1
0.1% TOLERANCE
R
REF
3.92kΩ
1
IOV
DD
V
DD
V
REF
3kΩ
10nF
1nF
RETURN
P1
P2
(4-WIRE)
THERMOCOUPLE
RTD
(3-WIRE)
NTC
10kΩ
3kΩ
CS
DIN
SCLK
DOUT
AV
SS
DGND
AIN6
AIN5
AIN4 (IOUT/VBIAS)
AIN3
AIN1
REFIN1(–)
REFIN1(+)
AIN0 (IOUT)
REFOUT
V
IA
V
IB
V
IC
V
OD
V
DD1
GND
P
V
DDP
GND
1
EN
1
V
OA
V
OB
V
OC
V
ID
V
DD2
V
ISO
V
SEL
GND
ISO
GND
2
EN
2
1nF
3kΩ
10kΩ
FERRITE
ADuM1441
AD7124-4
ADuM5010
FERRITE
16.9kΩ
10nF
0.1µF
10µF
10µF
+24V
3.3V
0.1µF
DIGITAL
INTERFACE
SDP
PMOD
OTHER
1µF
1nF
3kΩ
3kΩ
AVDD
I
EXC
AVDD
ADC
I
EXC
V
REF
DIGITAL
INTERFACE
SDP
PMOD
OTHER
ADP2441
DC-TO-DC
CONVERTER
GND
FIELD SUPPLY
13011-001
