Tested RS232-RS485 Converter

max232 and max485 schematic

I need tested, isolated or ESD/EMI
resistant RS232/RS485 full-duplex
schematic.

I am currently using MAX232 and MAX485s
with bias,termination resistors and TVS
diodes.

Which TVS diodes suitable for RS-232
and which are for RS-485?

Which parameter of the TVS is important while
selecting for RS232 and RS485.

Anyone could give a specific TVS part nr. from
any company? (IRF,Onsemi,General Semiconductor etc)

Best Regards

Probably this help you, it is in Italian..

https://www.vincenzov.net/progetti/rs485sw.htm


good luck :roll:

I don't have any schematic in my hand, but if you have MAX232 and MAX485 connected together, I think this is sufficient to good work.
My other ideas:
- for isolation, use transoptors, and isolated power supply (probably maxim makes IC and smd transformers for this - but I do not remember exact part numbers),
- look at the max voltage on MAX232 and MAX485 line input pins and use transils with that or lower working voltage (ie. lowest max input voltage for MAX232 is +/-15V - use 12V bidirectional TVS, for MAX485 max voltages are: -8/ +12,5V - use unidirectional transils for 7V and 12V),
- use IC's with letter E (ie. MAX485E, MAX232E); they are more resistant to ESD,
- I have used TVS from onsemi, because there are the fastest diodes all over the world
- exact part numbers: 1SMB12CAT3 (12V bidirectional), 1SMB12AT3 (12V unidirectional), 1SMB7.0AT3 (7V unidirectional)

A good site, with schematics, is https://www.rs485.com