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SN74AUP1G08: Pulling output Y while SN74AUP1G08 driving low

user4052185
Prodigy 230 points
Part Number: SN74AUP1G08

Hi,

is it possbile/acceptable to drive temporarily external voltage (3.3V) on output (Y) while SN74AUP1G08 itseld is driving LOW? 3.3V is applied to VCC while inputs A and B are LOW.

It seems to be working in logic wise that external voltage can change logic state of Y node HIGH even SN74AUP1G08 is driving LOW.

This would be used only few seconds is production phase of the product.

  • 0
    Guru 272320 points

    This is allowed, but only as long as the absolute maximum rating of 20 mA is not exceeded.

    AUP devices at 3.3 V have a typical output impedance of roughly 50 Ω, so you would need a series resistor of at least 120 Ω to make this safe.