AM26C31: short circuit protection

Milind Bapat

Part Number: AM26C31

I am considering using AM26C31 for RS422 driver. In order to enhance the short circuit protection mechanism, I am considering adding a small series resistance (20ohm) or PPTC following for 5.6V TVS diode. Is there any app note/ data, where TI recomends any such addition? Can somebody please guide me on this?

5 months ago

0 Ethan Sempsrott 5 months ago

TI__Mastermind 25682 points

Hi Milind,

What voltage are you trying to protect against? This transceiver can survive up to 14V shorts.

For general RS-485/RS-422 protection, you can use this guide: https://www.ti.com/lit/ug/tiduas1b/tiduas1b.pdf

As for the series resistance you can add 20 Ohms. Use pulse proof resistors to increase the chances of them actually protecting the transceiver.

Best,

Ethan

0 Milind Bapat 5 months ago in reply to Ethan Sempsrott

Intellectual 345 points

Thanks Ethan, the chips are supposed to work on 5V supply. So, if the outputs (all outputs) are shorted, will chip survive by limiting current at 170mA even without 20ohms? Alternatively, is adding PPTC instead of 20ohms better idea to ensure that the device sustains continuous shorting on all channels simultaneously?

+1 Ethan Sempsrott 5 months ago in reply to Milind Bapat

TI__Mastermind 25682 points

Hi Milind,

This transceiver will survive 5V shorts. This should not overwhelm the 170mA short circuit current since it is a lower voltage.

Note that the series resistors won't help that much with the current. TVS diodes and fuses (which I believe you are referring to with PPTCs) can be added for robust protection however. I also found a better guide for you to reference: https://www.ti.com/lit/ug/tiduer9/tiduer9.pdf

Best,

Ethan

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AM26C31: short circuit protection