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TCA9617A: Question about signal undershoot

Zhengquan Lu
Intellectual 1035 points
Part Number: TCA9617A

Hi team,

   The I2C link in customer's system is CPU---9617---9555. When customer use TCA9617 device and test from 9555 device port, they found the signal undershoot is about -630mV. The test result is attached. Could you please help to check and provide the solution? Thanks a lot!

Best Regards

Zhengquan Lu

  • 0
    TI__Guru 73541 points
    Hey Zhengquan,

    Some undershooting is expected from this device on B side (the side you are probing most likely). You can see this in figure 8 of the datasheet and again in figure 10 and 11. Side B has a fall time accelerator which will try to drive the signal to GND as fast as possible. The dips below ground are from your PCB trace having too much parasitic inductance. You can help limit the undershoot by adding a small series resistor on the B side (I would try 30 ohms or so). You could also try adding schottky diodes on SCLB and SDAB such as BAT54A.

    Thanks,
    -Bobby