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SN74VMEH22501A: B-port output pulled up to 5 V

Wei Hern Lok
Prodigy 40 points
Part Number: SN74VMEH22501A

Tool/software:

Can B-port withstand up to 5 V during output?

This part is 5-V tolerant but the voltage range applied to B-port output in the high/low state is only up to 4.6 V spec in absolute maximum ratings table? 

Which one should be the correct?

  • +1
    Guru 316690 points

    When a B-port pin is an output, it does not tolerate 5 V.

    Where does this 5 V come from? If there is a pull-up resistor, the difference between the output voltage and 5 V will be dropped over the resistor.

  • +1 in reply to Clemens Ladisch
    Prodigy 40 points

    Do you mind to share us how to calculate the pull-up resistance value to 5 V, if the output voltage required is 3.3 V?

  • +1 in reply to Wei Hern Lok
    Guru 316690 points

    The absolute maximum ratings would allow up to 50 mA through the pull-up, but you should stay away from that limit.

    In general, the value of a pull-up is a compromise between power usage and the speed of rising edges. If this does not matter, use 10 kΩ. (The speed matters if some device on the B-side bus uses open-drain signals. If the only purpose of the pull-up is to get a defined voltage when all other devices are inactive, it does not matter.)