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TCA9534A: Port pins have schmidt trigger?

Brian Antheunisse
Expert 5305 points
Part Number: TCA9534A

Team,

Customer is using this chip, we are wondering about the behavior on the port pins in terms of noise immunity/hysteresis, debounce situations, etc. The datasheet shows a VOH, and an IOL, which is a bit confusing. 

Thanks!

Brian

  • 0
    TI__Guru 72691 points

    Hey Brian,

    The device's output is controlled by two FETs seen below:

    The port pins DO NOT have any type of filtering/noise-immunity/EMI suppression, debounce features. It is just a push pull architecture that either pulls high (Q1 FET) or pulls low (Q2 FET).

    To try to ease the confusion, looking at section 6.5 of the datasheet where P Port VoL=0.5V means if you pull low (set the output to low) and probe the pin and see the Voltage is 0.5V (not fully GND) then a minimum of 8mA is flowing into the port. From this you can back calculate the Ron of the FET knowing the current and the voltage.

    On a side note our SDA/SCL does have a glitch filter internally (supresses glitches of 50nS).

    Thanks,

    -Bobby