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SN74LVC1G14: Schmitt Trigger Inverter Output state during power up/down

RuggedEngie
Intellectual 375 points
Part Number: SN74LVC1G14
Other Parts Discussed in Thread: SN74LVC1G126,

What happens to the output of this device during power up/down? I am using this device to control a critical signal and if the output signal is low at the wrong time it will cause problems. 

Thanks,

Mark

  • 0
    TI__Guru* 97046 points
    Hi Mark,
    If the input is held low, then the output is guaranteed to be high once Vcc reaches 1.65V.

    In my experience, these devices start operating around 1V, however this is not guaranteed by TI.

    If you need the output to remain high during the entire power-up ramp (ie all the way from Vcc = 0.001V up to 1.65V), I would recommend adding a device that has a 3-state output after the Schmitt-trigger inverter, then hold the the device in hi-z during startup with a pull-up on the output. An example device would be the SN74LVC1G126.

    If the OE pin for SN74LVC1G126 is held LOW with a pull-down resistor during the system startup, then the output is guaranteed to remain in high-impedance for the whole ramp. A pull-up to Vcc on the output would then ensure that the output was always at Vcc, regardless of the functional state of the SN74LVC1G14.

    Unfortunately, I don't know of a definitive solution with just 1 device.