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TUSB321AI - When power is off (VDD=0V) are the CC pins protected from downstream powered DFP devices?

Bob Fitch
Intellectual 345 points
Other Parts Discussed in Thread: TUSB321AI

In the TUSB321AI datasheet it says the voltage on the CC1, CC2 pins cannot exceed VDD + 0.3V.   What happens if you connect an un-powered DFP interface (VDD = 0V) to a powered downstream DFP interface that could have Rp pullups tied to 5V on their CC lines (or are the CC lines protected from this in ways not discussed in the datasheet?)

  • 0
    TI__Mastermind 36085 points
    Hello,

    I am reviewing your post and I will provide a feedback ASAP.
    Regards,
    Diego.
  • 0
    TI__Mastermind 36085 points

    Hello Bob,

        That shouldn't be an issue, since the TUSB321AI has the internal pull-downs and the connected DFP device must have a pull-up or current source which will drive the adequate voltage level to the TUSB321AI's internal Rd.

    Regards,

    Diego. 

  • 0 in reply to Diego Cortes
    Intellectual 345 points

    Diego,

    If a far-end DFP device has a nominal 56K pullup to 5V and the TUSB321AI has the nominal 5.1K dead-battery pulldown then the voltage on the CC pin on the TUSB321AI when VDD=0V will be approx 0.42V (and with worst-case tolerances it could be almost 0.6V) ... which exceeds the VDD + 0.3V absolute maximum spec in the datasheet for the CC inputs.  

    Is the in-series resistance protecting the CC input (i.e., if the input current is kept below some level it is OK to exceed the absolute maximum input voltage specs?)?

    Thanks,

    Bob F.

  • 0 in reply to Bob Fitch
    Intellectual 345 points

    Diego,

    Is there any further information for this (see the last Nov 28, 2015 6:46 PM post)?   If not we'll be using a different part with external VCONN power switches.  Thanks.

    Bob F.