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SN74AHC1G00: Will the output at high when Vcc drops?

David Huang
Intellectual 2285 points
Part Number: SN74AHC1G00

Hi

I'm using the 2 input NAND of SN74AHC1G00 with 3.3V of Vcc.

The input A is powered by a pull-up resistor to 3.3V while the input B is connected directly to 3.3V.

What I want to know is that if Vcc slowly drops from 3.3V, will the output be at high?

My understanding from the datasheet is that since VIH=Vcc×0.7, the output will not be high when Vcc drops, is that correct?

Thanks

David H.

  • 0
    Guru 317450 points

    When VCC drops, VIH also drops. If the input voltages do not change, they will still be above VIH.

    The inputs are overvoltage tolerant. If they are above VCC, they are still read as high, and the output is still low.