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SN74LVC3G07-Q1: Output when Input is 3.3V but Vcc is 0

John Louie
Prodigy 80 points
Part Number: SN74LVC3G07-Q1
Other Parts Discussed in Thread: SN74LVC2G17-Q1, SN74LV125A-Q1, SN74LVC3G07, SN74LVC3G34

Hello,

Will the output of this device be 0V when the Vcc is 0V while the input is set to 3.3V?

I saw that the device's input is rated for 5.5V, does that include when the device has a VCC of 0V?

Thank you,

John

  • 0
    TI__Guru 57490 points

    Hi John,

    Do you have external pullup resistors on this open drain device? The output will be at the pullup voltage level. Since this device supports Ioff, the output will not backdrive and power up the Vcc accidentally; the current leakage will be limited to not more than 10uA as listed in the datasheet.

  • 0 in reply to ShreyasRao
    Prodigy 80 points

    Hello,

    There will be a pull up resistor, but the pull up will go to a VCC which will be at 0V for the time being. 

    Is there a logic device you can recommend which I do not need a pull up for, but will not pass an output value when Vcc is off?

    I noticed that there are a few which are tri-state based. If Vcc is 0 but OE is on (meaning it will pass the signal) will the signal still be passed through or backfeed into the VCC?

    Thank you,

    John

  • 0 in reply to John Louie
    Guru 269770 points

    All little-logic devices in the LVC family have Ioff.

    There is no other automotive three-gate device; use multiple smaller one-/two-gate devices (SN74LVC2G17-Q1 or SN74LVC2G17-Q1) or a four-gate device from a different family (e.g., SN74LV125A-Q1).

  • 0 in reply to Clemens Ladisch
    TI__Genius 16725 points

    Hi John,

    The SN74LVC3G07 has the Ioff feature as clemens and shreyas have mentioned. When Vcc is 0V, the output will be Hi-Z. The output node will be floating if not connected to any voltage elsewhere. There is small leakage into the device as Shreyas has mentioned.

    As clemens has mentioned, there are no 3G's that are Q1 or automotive qualified. If you do not need an automotive device, then we have the SN74LVC3G34.

    Thanks!

    -Karan