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Original question:

TUSB320: TUSB320RWBR OTG auto detect

TUSB320: VBUS in DRP detection

user4999430
Prodigy 210 points
Part Number: TUSB320

Dear sirs:

As we've disscussed about the application of TUSB320RWBR in DRP detection, VBUS_DET  has to be kept  the sequence after the CC detection finish and the IC entered DFP/UFP mode,  as our product supports both USBC plug and POE power supply,  we have to add the anti backflow circuit to separate the POE output power and the VBUS. However,  we must also keep the PSU plug circuit from USBC CONN, a schottky diode can help, but create a voltage drop of PSU, sch shown as the attachment.

Do you have any suggestion about our design of power control, any better idea about the anti backflow circuit or any suggested IC that don't need to meet the VBUS_DET sequence？

thanks a lot

Sercomm RD Sally Feng

  • 0 in reply to user4999430
    TI__Guru 64326 points

    Hi,

    We do not typically see this kind of design and do not have a official recommendation. You cold increase the resitance on VBUS_DET to help limit some leakage current from POE_5V0.

  • 0 in reply to Malik Barton57
    Prodigy 210 points

    Dear sir:

    Actually, we've increased the detection resistor from 887k to >920k, that doesn't help.

    In our application, we support the power supply from both POE and PSU, if we don't add a schottky on USBC port to stop the reverse voltage from POE when powered by POE, the DRP mode can't work normally; but the schottky can cause a voltage drop when powered by PSU（USBC port）. So we want to figure out if we have any better detect solution for the TUSB320 based on our design, thanks

    Sally Feng 

  • 0 in reply to user4999430
    TI__Guru 64326 points

    Hi Sally,

    You mentioned that DRP connect work when powered by POE, could you explain more? You may consider using power switch instead of schottky. Power switch could provide more isolation and simplify your design.

  • 0 in reply to Malik Barton57
    Prodigy 210 points

    Dear Sir:

    Yes, when we powered the phone by POE, you can see VBUS would get a reverse voltage from VCC_5V0 through PMOS,  this voltage stops the detection of TUSB320.  BTW, what kind of power switch do you suggest? May I have your idea, thanks

    Sally Feng

  • 0 in reply to user4999430
    Prodigy 210 points

    Dear sir:

    Soft reminder, any suggestion?

    thanks

  • 0 in reply to user4999430
    TI__Guru 64326 points

    Hi,

    Sorry for the delay due to US Holiday. When powered by POE should phone be in UFP mode? Also I ma not a expert on power switches, so i recommend post on the power management forum about this leakage issue. The TPS229xx family seems like a good place to start depending on the maximum driver current provided by POE. 

  • 0 in reply to Malik Barton57
    Prodigy 210 points

    Dear sir:

    Thank you .

    And when powered by POE, the phone should also be in DRP mode, as the phone can be either a speaker or a host .

    Sally feng

  • 0 in reply to user4999430
    TI__Guru 64326 points

    Hi Sally,

    Is there any more support needed for this issue? If so please reply with any relevant details so that I can further assist you. For now I will be marking this thread as "TI Thinks Resolved". If you have resolved your issue, please post the solution to the original problem/post for others with similar issues.