SN74LVC245A: SN74LVC245APWR Back Drive

Mohammed Azlum

Part Number: SN74LVC245A

I'm using SN74LVC245APWR in my design. OE# (PIN 19) is always connected from one of the CPU active weak GPIO pin and it always drive even-though VCC (20th PIN) is powered OFF.
Is there any possible to back drive OE# pin if I connect the active GPIO before VCC (20th PIN) comes ?

Here I found one observation, OE# (PIN 19) driving low whenever VCC (20th PIN) is powered OFF. Is it expected observation ?

over 7 years ago

0 Emrys Maier over 7 years ago

TI__Guru* 97046 points

Hi Mohammed,
This device does not include positive input clamp diodes, so no, there is no way that an input driving at 3.3V will cause VCC_3V3 to be powered.

the OE# pin of this device is just an input - it cannot be driven by the SN74LVC245A. If the wire is being driven low, it must be coming from something else connected on the line.

0 Mohammed Azlum over 7 years ago in reply to Emrys Maier

Intellectual 835 points

OE# is input pin. Correct. It can sink the current also. Right ? Is it possible to Sink the strong current at OE# pin. Hence the wire is driving low ?

0 Emrys Maier over 7 years ago in reply to Mohammed Azlum

TI__Guru* 97046 points

No, the input does not sink current. It is a high-impedance CMOS input.

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SN74LVC245A: SN74LVC245APWR Back Drive