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SN74LVC2G17: IC behavior before Vcc is supplied

Antony Lin
Genius 13480 points
Part Number: SN74LVC2G17

Hi,

If "high level of input" is sent to input pins (1A and 2A) before Vcc is supplied, what would be the voltage level of output (1Y and 2Y)?  And will there be any leakage frmo 1A/2A to Vcc at this moment?

Thanks!

Antony

  • 0
    TI__Guru* 97046 points

    Hi Antony,

    The inputs of SN74LVC2G17 are over-voltage tolerant, meaning that they can have a voltage higher than Vcc without any problems. This is because there is no clamp diode from the inputs to Vcc.

    Because of this, the leakage from the inputs to Vcc will be extremely small (~pA range), as any leakage current would have to go through the gate oxide of the input MOSFETs.

    Your description of the Vcc pin is vague -- what does "before Vcc is supplied" mean?  Is that pin at 0V? floating? at some other voltage?

    If the supply pin is at or near 0V, then the outputs will be in a high impedance mode, as defined by the Ioff spec in the datasheet (10uA max leakage).

    If the supply is floating at or above the turn-on voltage for the MOSFETs (~0.8V), then the outputs would likely be at the supply voltage. We can't guarantee anything in this 'limbo' region, however, since the datasheet only defined the behavior of the part for Vcc = 0V and 1.65V ≤ Vcc ≤ 5.5V.