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TCA8418: Question about pullup resistors for Row/Col / GPIO pins

Part Number: TCA8418

Hi, just wanted to clarify about whether pullups are required or not.  In one place, the datasheet says to put pullups on unused inputs, whereas in another place it says that pullups are not required:

"Note that no external pullup resistors are needed, because the TCA8418 has integrated pullup resistors."

Note that we plan on using them as GPIO's (but assigning them to keypresses) and not Row/Columns, if that makes a difference.


  • Hi Michael,

    I believe the data sheet is talking about two valid points. One point is that you do not want to have any input left floating. A pull-up resistor would be required externally to keep a pin configured as an input biased to a known voltage level. See implications of floating cmos inputs here

    No external pull-ups are needed because TCA8418 has integrated pull-up resistors. These can be found in the registers 0x2C, 2D, 2E. 

    If the GPIO is configured to an output, the pin can be left floating with no pull-up/down resistance.