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TCA9555: Too fast falling time on I2C signal

Jason Dai
Expert 3720 points

Dear E2E,

Please help to check if 9.6ns falling time in I2C signal is accept or not.

It is already out of spec in the table below and help to double confirm it.

BR,

Jason

  • 0
    TI__Guru 72901 points
    Hey Jason,

    It's a little hard to see what your Vcc is but it looks like it is 3.3V which the timing requirement for FAST MODE states is a minimum of 12ns. In this case what you have measured seems to indicate that the fall time does not meet the I2C standard for FAST MODE.

    From the frequency you provided in the oscope shot it looks like you are in spec because there is no minimum fall timer requirement for I2C in STANDARD MODE.

    The table you took from the graph of our datasheet also is for fast mode and not standard mode.

    If you are having issues with the fall time being out of spec for fast mode, you can place a small series resistor on the SCL line infront of the master to slow down the fall time.

    Thanks,
    -Bobby