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TPS65982: Is it basically possible to "SWSr" without breaking data exchange?

Yevhen Horbenko
Intellectual 510 points
Part Number: TPS65982
Other Parts Discussed in Thread: BQ25713

Hello TI guys. I appreciate your help.

I'm developping a case when a Power Role has to be swapped to SRC. But I can't reach conditions when USB partners don't lose VBUS to not break data exchange.

I've tried to give out from BQ25713 to VBUS 5V 3A preliminarily or other voltages. But a current dongle is always displaying switch off and start again.

Thanks in advance.

  • 0
    TI__Expert 8680 points

    Hello,

    Yes, Power Role swap w/o breaking data is possible. Please note that both partners need to be self powered for successful Power role swap.

    Could you share the PD trace ?

    Thanks
    Prajith

  • 0 in reply to Prajith Cheerakkoda
    Intellectual 510 points

    I'm developing w\o tools to get the PD trace. Unfortunately.

    My developing device has an SSD onboard.

    A case is:

    The Board has been supplied by MacBook with TypeC-to-TypeC. Negotiating in 5V*3A contract. Initially DeadBatteryFlag is set.

    Before send SWSr I switch BQ25713 to OTG mode with 20V output. Making small delay in 11 sec.

    Send SWSr.

    But a current dongle blinks and detected before the SSD drive  by MacBook disappears from the MacOS Desktop.

    Can you recommend general steps to perform SWSr properly?

    Thank you guys.

  • 0 in reply to Yevhen Horbenko
    TI__Expert 8680 points

    Hello Yevhen,

    Please be aware that Vbus voltage will hit 0V during PR_swap. So I hope the SSD on the board is powered from battery or from barrel jack adapter.

    Thanks
    Prajith

  • 0 in reply to Prajith Cheerakkoda
    Intellectual 510 points

    The SSD is inside of the developed board. There's a battery onboard. The board comunicates TypeC-to-TypeC with MacBook.

    There's a case when the board's battery is depleted and MacBook supplies the board with power (the board PD gets DeadBatteryFlag set). The flag could be deleted with SW or it disappears after PD controller detects that is powered from 3.3V (for example from the battery via power supply unit after battery has been bit charged from another port).

    When board is ready to supply power to MacBook SW performs SWSr. And exactly in this moment data exchange stops. SSD is still supplied with a power on the board. But MacBook displays SSD ejecting. A current dongle is blinking once.

  • 0 in reply to Yevhen Horbenko
    TI__Expert 8680 points

    Hello Yevhen,

    Do you have a mux in the design? if yes, please check whether the PD controller modify mux control GPIO drive level. PD controller is  supposed to keep the data link/ MUX state intact during a successful PR_Swap event.

    In addition, please ensure PR_Swap is successful. If you don't have PD analyzer, you can capture scope trace of CC and Vbus to see PR_Swap waveform. 

    Thansk
    Prajith