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PCA9543A: When VCC is supplied, can VDPU0 or VDPU1 be power off?

user6143488
Prodigy 110 points
Part Number: PCA9543A


Hi,

I'm Sesumi from Japan.

I have a question about PCA9543A operation.

In my system, VDPU0 or VDPU1 can be power off  at a normal operation in which VCC is supplied.

That is acceptable for PC9543A?

If not acceptable, is it recommended to add pull-down to GND on SDA/SCL?

Best regards.

  • 0
    TI__Guru 53575 points

    Hi Sesumi-san,

    No pull-down is necessary on the downstream I2C lines in unpowered cases as long as the ports are disabled in this state. There may be disruption in communication if these pins drift far enough below gnd when the ports are disabled, however the unpowered slave devices on these lines will likely provide a strong enough bias to prevent this. Be sure that these ports are disabled before power is removed. Otherwise communication on the master SCL and SDA lines may not be possible.

    Let me know if you have any other questions or particular concerns regarding your application. 

    Regards,
    Eric

  • 0 in reply to Eric Schott1
    Prodigy 110 points

    Hi Eric-san,

    Thank you for your replying.

    I understand that it's necessary to disable I2c down-stream port before VDPU* are removed. 

    Your advice is so clear and helpful.

    Thank you !

    Regards,

    Sesumi