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TCA9555: Can the external pull up resistor not used?

Reagan Li
Prodigy 545 points
Part Number: TCA9555


Hi team, 

A quick question, can we just use the internal 100kohm for pull up and not use the external pull-up resistor if we can limit the output current for P07-P00 and P17-P10 below 80mA each and 160mA total ?

Thanks

  • +1
    TI__Guru 53575 points

    Hi Reagan,

    Yes, it is fine to rely on the 100k-ohm internal pull-up for the input pins. Make sure you consider the leakage paths that exist external to the device and the relatively slow rise-time of the signal if the signal driver goes high impedance from an output-low state (such as an open-drain output). 

    Note that this only really applies when the pin is configured as an input, as the pin will be push-pull while configured as an output. 

    Regards,
    Eric Schott

  • 0 in reply to Eric Schott1
    TI__Prodigy 545 points

    Hi Eric,

    Noted. Thanks for your detailed comments!