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PCA9543A: What is hot insertion?

Oliver Lin
Expert 3365 points
Part Number: PCA9543A

Tool/software:

Hi team,

Could you please help share some input what hot insertion is? And how this work? And what's the application?

"Does this device support D0/SC0 and SD1/SC1 only or does A0/A1 support hot insertion too?"

Thanks,

Oliver

  • 0
    Guru 268320 points

    "Hot insertion" means that you can connect a device to the bus while other devices are communicating.

    Please note that this requires that the channel where you are hotplugging is disabled.

  • 0 in reply to Clemens Ladisch
    TI__Expert 3365 points

    Hi Clemens,

    Does the A0/ A1 support hot insertion as well? Cause customer mentioned that they are putting the pull-up/ pull-down on other board to set different address.

    Thanks,

    Oliver

  • 0 in reply to Oliver Lin
    TI__Genius 13820 points

    Hello Oliver,

    Just to clarify what Clemens said hot insertion is only important on the SCL and SDA lines, 

    This is because if the device supports hot insertion on those pins then that will prevent any data errors that can happen during the insertion of the device onto the bus.

    Simply because  the SCL and SDA channels are hiz when the device is powered off and when the device receives power until a command is sent to connect a channel then that what prevents data error on the bus.

    Essentially hot insertion support only matters on the SCL and SDA lines of the device.

    This is a helpful app note that explains more. 

    Regards,

    kameron

  • 0 in reply to Kameron Hill
    TI__Expert 3365 points

    Hi Kameron,

    Thank you for your input, I see the most important on SCL and SDA, just wanna check with team that does our A0/ A1 also support hot insertion. Since customer design has put the address resistor on another board, that's why this question coming up, thank you.

  • 0 in reply to Oliver Lin
    Guru 268320 points

    The A0/A1 voltages can be changed, but if they change in the middle of an I²C transaction, it is undefined which address is actually used. You can do hot insertion on the A0/A1 pins only if you ensure that the PCA9543A itself is not being accessed at that time.

  • 0 in reply to Clemens Ladisch
    TI__Expert 3365 points

    Thank you, understood.

    Some other protection questions.

    We would like to know if there is any protective design on SDA/SCL for hot insert support. ex: ESD…

    If so, does A0 and A1 have the same design too?

  • 0 in reply to Oliver Lin
    Guru 268320 points

    No; the built-in ESD protection is designed only for what happens during automated assembly. Any signal that can be hot-plugged shout get more protection.