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short circuit protection for MAX3232ESE+

Other Parts Discussed in Thread: MAX3232

Hi all,

I need a short circuit protection for MAX3232ESE+ up to 28V for 2 min duration if its outputs get shorted with input supply lines which have +28VDC

How can I protect RX/TX lines of RS232 against short with supply lines. I have TVS diode protection but it can work only for short duration while it is needed for 2 min duration minimum.

  • Yogesh,

    The receivers in MAX3232 tolerate up to 30V.

    The drivers however are only rated to 13.2V

    The TVS should clamp less then that (certainly stay under 15V under any case)

    To help your TVS, add a little series resistance. Use less than 100 ohms to prevent data integrity issues.Using a thermistor instead of a resistor will help a lot.

    Otherwise you'll need to disconnect drivers with a relay to keep TVS from overheating.

  • Hi Ron,

    As I have mentioned TVS will work only up to few micro seconds while we have one test in which client will connect it to 28V for 60 seconds

    How can we protect this IC without affecting ICs life. following is the test client will do on the unit.

    Test 11 Short circuit protection All Outputs to be shorted with 27.5V for 60 Seconds

    Client specific requirement Class C Performance while Test   DV
    (Design Validation)
      N/A        
    -          
    PV (Production Validation) 0 PPAP parts      
    CC
    (Continuous conformance)
      N/A      
  • Yogesh,

    I understand that a TVS diode cannot shunt a power supply directly. However, the series thermistor (PTC) will also heat up and it's resistance will increase greatly. This will bring TVS current to safe level so the TVS will cool down and the thermistor will stabilize in temperature, albeit quite high.