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TCA6424: TCA6424 - VCCP pin 27

Dan Ringger
Intellectual 1790 points
Part Number: TCA6424

I am using the TCA6424 so that I can interface several 5v signals into my 3.3v TIVA CPU using I2C.

 

   If the 5v supply on the VCCP pin 27 were to suddenly be at zero volts and the VCCI pin 31 were to stay at 3.3 volts,

 

will the chip tolerate that for long periods of time and will there be any increase in 3.3v current?

 

    My customer wants be to change the design slightly to run on a 3.3v battery powering the CPU and all other 3.3v devices. So the processor stays powered up but the 5v components will be at zero volts during a power down event.

 

     Basically they want the cpu and all other 3.3v devices to be alive during a power outage.  They may see power outages as long a 72 hours.

  • 0
    TI__Guru 63230 points

    Hey Dan,

    "will the chip tolerate that for long periods of time and will there be any increase in 3.3v current?"

    This doesn't sound like an issue. The output stage of the device will no longer work because there is no bias voltage to turn on the FETs on the output. While the input stage will remain high impedance.

    Is the customer planning to communicate to the IO expander while VccP is GND?

    Thanks,

    -Bobby