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TPS25751: Unplugging USBC sometimes cause TPS25751 being not able to become APP mode

Hideki Hayashi1
Expert 8720 points
Part Number: TPS25751


Tool/software:

Hi team,

Customer noticed TPS25751 returns PTCH mode when USBC(with 9V source) is unplugged in specific case.

1. Plug USBC(with 9V source) => Equip Battery => Unplug USB (it trigger returning PTCH)

READY_FOR_PATCH interruption occur.

TPS25751 doesn't returns PTCH mode when....

2. Equip Battery => Plug USBC(9V) => Un-equip battery  => Equip battery => Unplug USBC(9V)

3. Anytime with USBC(with 5V source)

Entering PTCH mode take over 300ms, so customer wanted to avoid it.

Has this phenomenon observed before? What will be taken for this?

Block diagram

Regards,

Hayashi

  • +1
    TI__Mastermind 35146 points

    Hi Hayashi-san, 

    Hideki Hayashi1 said:

    1. Plug USBC(with 9V source) => Equip Battery => Unplug USB (it trigger returning PTCH)

    READY_FOR_PATCH interruption occur.

    TPS25751 doesn't returns PTCH mode when....

    In this first step when the battery is equipped after 9V USBC source is plugged, is the entire system not powered including TPS25751? Specifically is TPS25751 booting up in dead battery mode (VBUS comes up first and then VIN_3V3)? If that is the case, is the EC clearing the dead battery flag anytime after the battery is equipped and before the 9V USBC source is disconnected? 

    If TPS25751 first boots up in dead battery mode and the DB flag is not cleared, removing VBUS will temporarily cause TPS25751 to disconnect and lose power since internally it is still receiving power from VBUS instead of VIN_3V3. To avoid this ~300ms delay the EC needs to clear the DB flag using 'DBfg', this will allow TPS25751 to switch over it's internal power source from VBUS to VIN_3V3 instead. 

    Thanks and Regards,
    Raymond Lin