Transcript
Application Note: AN-111
INTEGRATED CIRCUITS DIVISION
Isolated 0-10V to 4-20mA Converter Application
AN-111-R02
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Application Note: AN-111
INTEGRATED CIRCUITS DIVISION
The LIA100P, with a typical Common Mode Rejection Ratio of 130dB (see Figure 1A) and isolation voltage up to 3750V is a good choice for this kind of application. CMRR - Rejection Ratio (dB)
Common Mode Rejection
Industrial controllers and data acquisition equipment frequently require an isolated voltage-to-current loop converter in environments where high common mode noise exist and protection of equipment and personnel from high voltages are required. The current loop, usually 4-20mA, is used to drive control valves or the input to chart recorders for temperature/pressure monitoring over time for example. Figure 1 shows a simplified block diagram of an isolated pressure transmitter.
-80 -90 -100 -110 -120 -130 1
10
100
1000
Frequency (kHz)
Figure 1A. The example circuit for this application is shown in figure 1B. The LIA110P is in the photovoltaic mode which has linearity comparable to a 13-14 bit D/A converter with 1 LSB nonlinearity or 0.01% of full scale.The result is a clean, linear conversion from 0-10V to 4-20mA as shown in figure 2. IOUT vs. VIN
Isolated V-I Converter
Pressure Transducer
-70
0.1
Isolated Power Supply
Power Supply
-60
20 18
4-20mA
16
I OUT (mA)
Signal Conditioner
Recording Instrument
0-10V
14 12 10 8
VCM
6 4
Common mode voltage VCM of 3750Vrms
0
1
2
3
4
5
6
7
8
9
10
VIN (Volts)
Figure 1. Isolated Pressure Transmitter
Figure 2.
RIN
CF
+ VCC
VCC RLED
1 2 3 4 5 6 7 8
+
+
Isolated VCC2 Power Supply
VCC2
LIA110P 16 15 14 CF 13 V CC2 12 11 10 9
R4 RF
VCC2 U2 +
VCC2
VCC2
U3 +
Q1
Non-isolated VCC Power Supply
12.5V
12.5V
IOUT RL
C2
U1 Note: For single power supply:
= VEE1
= VEE2
Figure 1B. 0-10V to 4-20mA Converter
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R02
INTEGRATED CIRCUITS DIVISION
Application Note: AN-111
For additional information please visit our website at: www.ixysic.com IXYS Integrated Circuits Division makes no representations or warranties with respect to the accuracy or completeness of the contents of this publication and reserves the right to make changes to specifications and product descriptions at any time without notice. Neither circuit patent licenses nor indemnity are expressed or implied. Except as set forth in IXYS Integrated Circuits Division’s Standard Terms and Conditions of Sale, IXYS Integrated Circuits Division assumes no liability whatsoever, and disclaims any express or implied warranty, relating to its products including, but not limited to, the implied warranty of merchantability, fitness for a particular purpose, or infringement of any intellectual property right. The products described in this document are not designed, intended, authorized or warranted for use as components in systems intended for surgical implant into the body, or in other applications intended to support or sustain life, or where malfunction of IXYS Integrated Circuits Division’s product may result in direct physical harm, injury, or death to a person or severe property or environmental damage. IXYS Integrated Circuits Division reserves the right to discontinue or make changes to its products at any time without notice.
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Specification: AN-111-R02 ©Copyright 2014, IXYS Integrated Circuits Division All rights reserved. Printed in USA. 4/7/2014
