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BQ25790: OTG operation

Hailiang Zhang
Expert 6905 points
Part Number: BQ25790

Tool/software:

Hi Team,

When OTG is working and the input is connected to Vin , what is the behavior of the device and are there any risks? Thanks!

Regards,
Hailiang

  • 0
    TI__Guru**** 154276 points

    Hi Hailiang,

    The IC has no way to know if an adapter with voltage <= OTG-OVP threshold is plugged in.  So, it will stay in OTG mode and provide power back to the adapter.  There is little risk to the charger but not sure what the adapter will do. If the adapter cannot sink current, the VBUS pin will increase causing OVP event.  The OVP event turns off the converter and wants for the OTG output to drop to restart.  So, the input would likely have a triangular oscillation.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    TI__Expert 6905 points

    Hi Jeff,

    If the adapter cannot sink current, the VBUS pin will increase causing OVP event.
    May I know why the OVP event will occur?

    Regards,
    Hailiang

  • 0 in reply to Hailiang Zhang
    TI__Guru**** 154276 points

    If Hailiang,

    When the adapter is providing a voltage and can't sink current and the charger is also providing a power at the same node, the capacitance at VBUS could overvoltage especially if charge PFM mode is disabled.  If that voltage on VBUS capacitor exceeds the threshold below, the converter turns off and reports OTG_OVP in the fault register.

    Regards,

    Jeff