Figure 21. Full Duplex Point-to-Point Current Loop System Configuration.
Figure 22. Half Duplex Current Loop System Configurations for (a) Point-to-Point, (b) Multidrop.
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Data subject to change. Copyright © 2005-2010 Avago Technologies. All rights reserved. Obsoletes AV01-0541EN
AV02-2353EN - February 8, 2010
of common mode influences, elimination of ground
potential differences and reduction of power supply re-
quirements. With this combination of HCPL-4100/-4200
optocouplers, specific current loop noise immunity is
provided, i.e., minimum SPACE state current noise im-
munity is 1 mA, MARK state noise immunity is 8 mA.
Voltage compliance of the current source must be of an
adequate level for operating all units in the loop while
not exceeding 27 V dc, the maximum breakdown voltage
for the HCPL-4100. Note that the HCPL-4100 transmitter
will allow loop current to conduct when input V
CC
power
is off. Consult the HCPL-4100 transmitter optocoupler
data sheet for specified device performance.
For more information about the HCPL-4100/-4200 opto-
couplers, consult Application Note 1018.
