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P82B96: undershoot - is Schottky diode required

Part Number: P82B96


I am using PB96 for I2C communication on 3m cable. I have undershoots ~ -700 mV on SDA and SCL lines. I added BAT54C schottky diodes to protect the P82B96 from exceeding absolute maximum ratings. Undershoots were reduced to ~ -500 mV (still higher than -0,3 V abs max).

My question is if the undershoots may damage the P82B96? I checked also datasheet of P82B96 from NXP and they show clearly that absolute max ratings at TX, RX lines are DC values only, and short spikes on I2C lines do not lead to any problems and do not need to be clamped. Is it also the case for P82B96 TI? - in other words - is it allowable to have short undershoots exceeding absolute maximum values?

Best regards,

Jakub Kwolek

  • Jakub,

    This should not be a problem. Absolute maximum ratings are there to limit the the voltage/current on pins based on the design process used, and are not necessarily a guarantee that the device will be damaged. But ultimately, it's dependent on the power delivered to the pin, not just the voltage. Short negative voltage spikes won't damage the device, but may cause adverse functional effects. I've notified our I2C expert to comment further.


    Eric Hackett