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MAX3221: TVS Diode Selection for RS-232 Output Lines

Venkata Rami Reddy Vempati
Prodigy 120 points
Part Number: MAX3221
Other Parts Discussed in Thread: ESDS552

Hi Team,

Regarding the TVS diode selection for the RS-232 output lines:

image.png

The receiver voltage rating is ±25 V, and the driver voltage rating is ±13.2 V. Based on these ratings, I would like to clarify the following:

  • Should i select separate TVS diodes for the Driver and receiver lines based on their respective voltage ratings?
  • Is a 14 V breakdown voltage TVS diode suitable for both the driver and receiver lines, or should I select the TVS diode based on the voltage rating of each line

Please advise on the correct TVS diode selection for this interface.

Thanks & Regards,
Rami Reddy

  • 0
    TI__Genius 17222 points

    Hi Rami,

    This is a good question. The simple answer is that a 12-14V working voltage is acceptable for all RS-232 lines (generally <13V breakdown voltage). The typical RS-232 driver output is around ~5V to 6V in reality. But in the case of significant noise or GND shifts, the receiver has a much larger input range so it can still read the incoming signal. 

    We typically recommend the ESDS552 protection diode which has 30kV contact protection and 600W surge protection. It has a breakdown voltage starting at 13.2V. 

    Best,

    Ethan