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  1. #1
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    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

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  2. #2
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    Re: Tested RS232-RS485 Converter

    Probably this help you, it is in Italian..

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


    good luck



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  3. #3
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    Re: Tested RS232-RS485 Converter

    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)
    arturt134



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  4. #4
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    A good site, with schematics, is http://www.rs485.com



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