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Simplified Buttons (up to 24)

Mauricio Solis Jr
Prodigy 645 points
Other Parts Discussed in Thread: TCA8418, TCA8418E

Hi team,

I'm having a difficult time understanding the TCA8418's datasheet. 

On Page 29, the keypad arrangement is shown without resistors.  I am confused about how the pins are configured as outputs and I don't know if there are limitations.

What are the recommended row/column interface?

I require a simplified button interface of up to 24.

Thank you,

Mauricio Solis

  • 0
    TI__Genius 16510 points
    Hello Mauricio,

    Thanks for your question.

    First off, is there a reason you're looking at the TCA8418 instead of the TCA8418E?
    I would recommend you look at the TCA8418E, since it has higher ESD protection rating and also has the erratas fixed from the TCA8418.

    Another bonus is that datasheet update that I just finished is online for the TCA8418E (and soon the non-E as well), where I tried to be very clear about the features of the device.


    The way the keypad works, is that the rows are configured as inputs with internal pull-up resistors enabled (keep in mind that the device features internal pull-up resistors), and the columns are configured as outputs, driven low. When a button is pressed, it will short a row and column together, and the input will see a falling transition, letting the device know to start searching for a key press.

    Are your 24 buttons to be multiplexed? I assume you are planning on doing a multiplexed keypad