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TCA9517: TCA9517 bus B low level is not low enough

doug lin
Prodigy 10 points

Part Number: TCA9517
Other Parts Discussed in Thread: TCA9803

Hi teams,

The bus B low level of the measured waveform is about 0.56V. Generally, the low level of the I2C signal is very low. It doesn’t feel good if the low level is not low enough.
Will this affect the communication of the next-level equipment?
  • +1
    TI__Guru* 78901 points

    Hi Doug,

    30% of Vcc is the ViL threshold for I2C devices. VccB lowest recommended value is 2.7V for this device (TCA9517) which gives a number of 0.81V which gives quite a bit of margin against the static voltage offset on B side of 0.6V max. Any I2C compliant device will accept this as a logic low.

    The only situation I can think of where this could cause issues is if B side is connected to any large series resistances or other static voltage offset buffers.

    -Bobby

  • +1
    Guru 321490 points

    If you want low voltages on both sides, use a different buffer like the TCA9803 (which has different restrictions).