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SN74LVC245A: SN74LVC245A in Mixed Voltage during Power-Up

AP
Intellectual 370 points
Part Number: SN74LVC245A

Hello,

a question regarding using the 74LVC245A (3.3V VCC) in a 3.3V, 5V mixed voltage application. Power-Up sequence is: 5V first, 3.3V a bit later.

Because of partial power-down suppport, the 74LVC245A keeps its outputs disabled while the 3.3V are not quite up (I guess). The inputs are 5V tolerant while the device is powered.

But what about the inputs (control and/or data) while the device is not powered? Is it OK to have active 5V signals applied to control and/or data inputs of the 74LVC245A while the 3.3V supply isn't up? Any internal diodes from pins to VCC?

Thanks

  • 0
    TI__Expert 6680 points

    Hi,

    Because of partial power-down suppport, the 74LVC245A keeps its outputs disabled while the 3.3V are not quite up (I guess). The inputs are 5V tolerant while the device is powered. That is correct, this device supports live insertion.

    But what about the inputs (control and/or data) while the device is not powered? Is it OK to have active 5V signals applied to control and/or data inputs of the 74LVC245A while the 3.3V supply isn't up? Any internal diodes from pins to VCC? This should be fine, there are no diodes from the inputs to VCC on this device.

    Thanks!

    Chad Crosby