Specifications

Chapter 4 - Transient Protection of RS-422 and RS-485 Systems RS-422 And RS-485 Applications Ebook
Page 61 of 137 Manual Documentation Number: <DocNumber>
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The following diagram shows an isolated RS-232 to RS-485 converter
with TVS devices from both signal lines to ground. This method is
recommended. Isolation protects the circuit from any voltage drops in
the earth ground connection. The shunt devices prevent a surge from
exceeding the breakdown voltage of the isolators as well as handling
any differential surges on the cable.
Figure 45: Isolated node with shunt protection to earth ground