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TXS0108e as isolating device

John Merrill
Intellectual 420 points
Other Parts Discussed in Thread: TXS0108E, MSP430F5244

I need to isolate my UART to USB bridge chip (FTID FT232RQ) from my MSP430F5244 so that power does not back feed in my circuit and cause the device to not shut down.  I have 65 lines that power could inadvertently be transferred through.  Can I use the TXS0108E to solve this issue?  I would drive VCCb (3.3VDC) from the processor side, and VCCa (3.3VDC) from the USB.  The OE pin would also be driven from USB side.  So if the device is on and not connected to the USB, no communications should occur and no power should be transferred the FTDI chip.  When the USB is plugged in, the FTDI chip is powered, and the TSX0108E will turn VCCa and OE on allowing communications.

Will this work or is there another device i should use.  

Thanks.

  • 0
    TI__Guru 55990 points
    Moving to translation forum .
  • 0
    TI__Genius 16430 points
    Hello John,

    THanks for the question.

    To be clear, you are asking if you can use the TXS0108E to disconnect the communication channel? In some sentences, it sounds like you are trying to use the TXS0108E to supply power to the FTDI IC, which won't work.

    If you are only looking to disconnect a communication channel between the FTDI chip and the MSP430, then what you have outlined should work (tieing the VCCA and OE to the power rail for the FTDI chip).

    Do you have a block diagram or rough sketch you could show? That would make it easier to see what you're trying to do.

    Regards,
    Jonathan