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TCA6408A: I2C line to Low state during RESET initialization

Toshiro Imi
Expert 7260 points
Part Number: TCA6408A

Hello,

Our customer has a question about I2C signal line condition in TCA6408A RESET initialization process. Could you let us know whether you experienced pulling I2C line low during RESET initialization process.

Best regards,

  • 0
    TI__Guru 73971 points

    Hi Toshiro,

    What exactly do you mean by the I2C line going low during RESET. Do you mean the device is already powered up and then you toggle reset and see SDA go low for a moment?

    -Bobby

  • 0 in reply to BOBBY
    TI__Expert 7260 points

    Hi Bobby,

    Thank you very much for your quick reply.

    We could not get our customer exact use case though, would it be possible to let us know following two cases.

    1. Device is already powered up then toggle /RESET.

    2. during Power up with /RESET=Low.

    Best regards,

  • 0 in reply to Toshiro Imi
    TI__Guru 73971 points

    Hi Toshiro,

    Toshiro Imi said:
    1. Device is already powered up then toggle /RESET.

    This should be fine, I've never heard of any issues with this situation occur before.

    Toshiro Imi said:
    2. during Power up with /RESET=Low.

    This should also technically be okay.

    There is one case that we've seen some troubles with. It doesn't have to do with the #RESET but instead the power sequencing of TCA64XX. I believe Vccp needs to power up before Vcci or in some cases the SDA can lock until both power supplies are up. I'll need to double check on the power sequence to be sure but we are planning to update the datasheet to state this in the power supply section as well as issue a PCN when the change is made. 

    -Bobby

  • 0 in reply to BOBBY
    TI__Expert 7260 points

    Hi Bobby,

    Thank you very much. I understood.

    Regarding to VCCI, VCCP power sequencing, would you let us know the secure way that will not happened SDA lock condition that are known at this moment.

    best regards,

  • 0 in reply to Toshiro Imi
    TI__Guru 73971 points

    Hi Toshiro,

    I spoke with our design team. We suggest VCCP powers up before VCCI (or at same time as VCCI). This will be updated in our datasheet a bit later. 

    -Bobby

  • 0 in reply to BOBBY
    TI__Expert 7260 points

    Hi Bobby,

    Thank you very much. The customer informed that VCCI and VCCP power up simultaneously, so I suppose this customer does not face on any issue.

    Best regards,