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TCA8418: Schematic Review

Ryu Yamashita
Expert 2570 points
Part Number: TCA8418

Hi team,

I am trying to implement this device with the attached circuit using an external pull-up.
The internal pull-up will be turned off with a register.
Is there any problem?

Also, am I correct in thinking that in keyscan mode, internally col is working as an output pin and row as an input pin?

Sincerely,
Ryu.

  • 0
    TI__Mastermind 32063 points

    Hi Ryu,

    No problem in turning off the internal pull-up resistors. External pull-ups here will work just fine, however, I think internal pull-ups will be needed on the ROW pins set to input. When the COL outputs a LOW signal and a button is de-pressed, the ROW pin will receive a logic LOW, however when the button is released, there is no way for the ROW input pin to rise to a logic HIGH voltage unless a pull-up is present on the pin internally or externally. 

    Ryu Yamashita said:
    Also, am I correct in thinking that in keyscan mode, internally col is working as an output pin and row as an input pin?

    yes I believe this is correct. 

    Regards,

    Tyler