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TCA6416A: Do all I/O pins have built-in Schmitt triggers?

Tatsuya Yamamoto
Prodigy 30 points
Part Number: TCA6416A
Other Parts Discussed in Thread: TCA9555

Tool/software:

Hi,

I'm considering adopting the TCA6416ARTWR.

Do all I/O pins have built-in Schmitt triggers?

OR, only SDA/SCL have?

Thanks,

Tatsuya

  • +1
    TI__Mastermind 47008 points

    Yamamoto-San,

    SDA and SCL of our I2C IO expanders use CMOS inputs with minor hysteresis. The signal is then filtered as required by the I2C specification for 50 ns glitches (only I2C target devices have this and require this). 

    The Pxx pins can be configured to high-z CMOS inputs. I don't believe they have Schmitt trigger inputs on the IO side. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 30 points

    Hello Tyler,

    Thank you for your answer.

    I’m concerned about the rise-up time to Pxx pins when using it as an input pin with a pull-up resistor (47kΩ).

    The circuit is shown in text below.

    [TCA6416A]<---[Protection resistor in series(1kΩ)]<---[Decoupling capacitor b/w GND(0.1uF)]<---[Pull-up resister b/w 3.3V]<---[Physical switch(Open or GND)]

    I think the rise-up time will be on the order of milliseconds.

    Will not the TCA6416A fail or go into a fault state even with this millisecond input?

  • +1 in reply to Tatsuya Yamamoto
    TI__Mastermind 47008 points

    Yamamoto-San,

    Rise time on the order of milliseconds is okay. 

    TCA6416A does not have a fail / fault state. This rise-time is okay. 

    For example, TCA9555 has internal 100k PU resistors. This device operates just fine with large rise-times. The same is true for the TCA6416A. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 30 points

    Hello Tyler,

    Thank you so much！

    I understood.