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Debounce setting for TCA8418

acelebi
Prodigy 20 points
Other Parts Discussed in Thread: TCA8418

Dear Madam \ Sir,

I'm using TCA8418 in Keypad mode. It is written that max debounce time is 60ms in the datasheet. Can I change debounce time duration? If yes, how can I change it? I could not see any information in the datasheet.

Best Regards,

Aziz

  • 0
    TI__Guru 62050 points
    Hi Aziz ,
    The engineer associated with this part has been notified for resolution.
  • 0
    TI__Genius 16510 points

    Hello Aziz,

    The debounce time for the TCA8418 is not adjustable. The typical value of debounce is ~50us and the variance is to account for any differences in device to device.

    Please also note that the devounce registers, when set to 0, debouncing is enabled. The debounce register is labeled as the "debounce disable" register, meaning that if it is set to 1, then debounce is disabled.

  • 0 in reply to Jonathan Valdez
    Prodigy 20 points

    Hi Jonathan,

    Debounce time is written 50 us in the datasheet. Which one is true? 50us or 50ms?

    In the EMI test, TCA8418 sends that keypad pressed while there is no touch on keypad. Do you have any idea to prevent this?

    Best Regards,

  • 0 in reply to acelebi
    TI__Genius 16510 points
    Acelebi,

    50 us is the correct value. I've updated my post to reflect that.

    Typically, in an EMI test, (specifically the negative EMI tests), the voltage on the pin swings negative to the point where the ESD cells will come on and clamp the voltage. The 50us debounce should take care of this, provided they are enabled.

    If you find that your EMI tests activate random button presses, I would double check the debounce_disable registers and make sure they are all set to 0x00 (0 = debounce on, 1 = debounce off).

    If you are still having issues, you are likely swinging negative for longer than 50us, in which case, additional capacitance on the node might help, depending on your amplitude of EMI.