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TMS320F28075: Shared Pull-up resistor for multiple unused GPIO

Brian Wang0
Expert 5390 points
Part Number: TMS320F28075


Hi team,

Customer would like to used one shared pull-up resistors for 2~5 unsed GPIO. Any protential problem from your side? What is the recommended value?

Regards,

Brian

  • 0
    TI__Mastermind 42195 points

    Brian,

    if the customer is trying to save components please remember that there are three acceptable practices for unused GPIOs:

    1. No connection (input mode with internal pullup enabled)
    2. No connection (output mode with internal pullup disabled)
    3. Pullup or pulldown resistor (any value resistor, input mode, and with internal pullup disabled)

    So they have the option to not connect any external pull-up or pull-down resistor. If they use an external Pull-up resistor, a larger value should be OK(10K or even a little larger), as long as they configure it as an input. This is only to keep the pin from drifting to a mid-rail voltage.

    Regards,
    Cody 

  • 0 in reply to Cody Watkins
    TI__Expert 5390 points

    Hi Cody,

    Understand they would have 3 options. But pull-up resistor is part of their design guidance.

    If they would like to share pull-up resistors, is it acceptable and what is the recommended value?

    Regards,

    Brian

  • 0 in reply to Brian Wang0
    TI__Mastermind 42195 points

    Brian,

    sharing a Pull-up should be OK for GPIOs 2-5. Please use a value around 10-20K.

    Regards,
    Cody