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TCA8418E: Can we tie all unused COL & ROW pin together and use only one pull up(10Kohm) to VCC?

Andy_Lin
Intellectual 2230 points
Part Number: TCA8418E

Hi Team,

I would like to ask , for TCA8418EYFPR , as datasheet specify the unused COL and ROW pin should tie to VCC with an pull up  resister.

however , my question is , if we have several COL , ROW pin unused, can we tie all unused COL & ROW pin together and use only one pull up(10Kohm) to VCC? Is there's any concern on this?

please kindly help for suggestion , thanks a lot!

  • 0
    Guru 243910 points

    If one of the pins would actively drive low, all connected input pins would read low. But that can happen only when you configure those rows or columns as enabled.

    With a correctly configured device, the unused pins can share a pullup.

  • 0
    TI__Mastermind 49270 points

    Hey Andy,

    If the unused pins are configured as part of the keypad matrix, then you will end up filling/overflowing your FIFO with garbage data because the rows see the col go low every 2 strobe cycles.

    If the unused COL/ROWs are set as inputs, then this is okay. It all depends on how you configure the device.

    -Bobby