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ADUM1234 and ADUM3221 Input Signal Rise and Fall Times

Category: Datasheet/Specs
Product Number: ADUM3221 and ADUM1234


What happens if the rise/fall time of the input signal for the ADUM3221 or ADUM1234 is longer then the recommended maximum in the datasheet?

Will it just possibly oscillate until it reliably gets out of the hysteresis zone?

Will it reliably hold the appropriate output voltage once the input voltage is well out of the transition zone?

We want to use these devices to quickly turn off a floating FET in an industrial safety interlock application.

The rise time would usually be much less than 1m as the deadline is around 50us (to turn the FET off), but if for some reason the signal should rise slow the output should, at least, still eventually reach the desired level reliably.



  • Hello Adam,

    The datasheet specify 1ms as recommended Input Signal Rise and Fall Times, however this parameter is only recommended but not critical.
    If the transition is slower than the recommended transition time, the output will hold the appropriate value until the input signal cross the appropriate threshold.
    The hysteresis zone will prevent oscillations, please refer to "Logic High Input Threshold" and "Logic Low Input Threshold" in the datasheet for the definition of the hysteresis zone.