ADM2587E max allowable voltages on RS485 pins

Document created by analog-archivist Employee on Feb 23, 2016
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We're looking to use the ADM2587 part in a product that we currently
manufacture in volumes of around 1k/qtr. We want to replace our existing
non-isolated RS485 chip with this part in an attempt to reduce the failure rate
due to bad wiring. The installers frequently connect the 24V supply to the
RS485 pins, and this destroys the chip.

My question is; "What is the maximum allowable voltages on the RS485 pins
(A,B,Y,Z), relative to each other?". The datasheet goes into detail regarding
the isolation, and mentions the 15kV ESD protection on these pins. It also
mentions test parameters of -7/+12V, but makes no mention of a maximum
continuous voltage.

In our situation, it's likely that 24V (AC or DC) will be applied between A & B
(or Y & Z), and I need to know if the ADM2587 will survive this condition
reliably, and ideally, what the maximum safe voltage would be.

 

The absolute maximum continuous voltage on the ADM2587E A, B, Y, and Z pins is
−9 V to +14 V.
Outside the −9 V to +14 V limits the device may be damaged permanently.

We are currently working in this space – high voltage miswiring to bus pins,
EFT, ESD, and Surge.
We currently have a certified EMC compliant reference circuit if you also
require protection against Surge (IEC 61000-4-5), EFT (IEC 61000-4-4), and ESD
(IEC 61000-4-2) ?
The Circuit Note CN-0313 includes a reference for lightning surge protection,
and the associated technical article discusses in detail some of the
considerations that were taken into account when designing this for the
ADM3485E.

EMC-protected RS-485 page:
http://www.analog.com/rs485emc

Circuit Note CN-0313:
http://www.analog.com/en/circuits-from-the-lab/cn0313/vc.html

Technical Article MS-2443, Safeguard your RS-485 Communication Networks from
Harmful EMC Events:
http://wwwp.analog.com/static/imported-files/tech_articles/Safeguard-Your-RS-485
-Communication-Networks-from-Harmful-EMC-Events-MS-2443.pdf

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