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BQ25628: Wont turn on after entering ship mode

Dajgoro Labinac
Prodigy 30 points
Part Number: BQ25628

Hello

We have a product that we switched to the BQ25628 PMIC. We got everything working properly, but there is an issue with QON and the ship mode.
Sometimes after customers use the product, some devices get stuck in a limbo mode where they cannot be woken up by QON or charging.
The pullup on the QON pin is rather weak, so we ended up bodging it with a 20k pullup since I saw one device with fluctuating voltage on the QON switch.
Even with that we had a case where a device just froze in a off state, and whenever I take it apart to inspect it (I have to disconnect the battery) it resolves the issue.
What could be causing such a rare intermittent issue of freezing the pmic in a off state (holding it 8 sec has no effect).
The schematic is basically the reference one, with an added NPN on the QON so it can be activated by an external signal.
It is also picking up the button press for the mcu.



  • 0
    TI__Guru 57321 points

    Hi,

    1. What do you mean " they cannot be woken up by QON or charging"?

    2. After adding a 20k pullup (R3), the device may exit ship mode by QON or adapter plug-in?

    Thanks a lot,

    Ning.

  • 0 in reply to Ning T
    Prodigy 30 points

    Hi
    1. The pmic does not leave ship mode, there is no power on the output side. Even after holding it for 8 sec. So far I only saw one board with the extra resistors do it, and disconnecting and reconnecting the battery always fixes this issue.
    2. There was this very weird issue where devices would return as defective, but each time we would take them apart to analyze they would work perfectly.
    I did manage to catch one on the act and the voltage on the QON pin was fluctuating randomly. I could not explain how or why, but since then we had been adding this extra resistors to force it high. The internal pullup on QON is 250k which is rather high to start with.

  • 0 in reply to Dajgoro Labinac
    TI__Guru 57321 points

    Hi,

    1. After adding the 20k pullup (R3), the device may exit ship mode for most of the times but not always, right?

    2. Could you please provide the step-by-step test procedure from entering the ship mode to not exiting ship mode?

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 30 points

    Hi
    1. The issue was present before adding the pullup, the pullup seems to had fixed the majority of the problems (maybe even all, but we did have one board so far that had an issue still, in theory it could had been something else).
    2. There is no rule, we test all the devices before shipping and they all work fine, but after a while the some clients reported they could not power on anymore and we have them shipped back. Sometimes they would come back and work just fine, but every time we would disconnect the board from the battery it would resolve the issue. Sometimes even loosening the housing screws would fix it (I suspected poor soldering but I was never able to find anything wrong with it, it was all done at a pick and place fab, also if it had soldering issues we would have other problems too). A few rare boards would have the issue persisting and that is where I managed to see with a oscilloscope that the voltage was fluctuating on QON (fluctuating on a low frequency, sub 10hz in a brownian motion style).
    As I said, there would be no rule, it was not something we could recreate, but I was able to simulate it by literally soaking the board in water (that would cause currents to go in and out of QON).
    So my question is, could I had missed something in the design? Is there an errata bug that I didn't figure out?

  • 0 in reply to Dajgoro Labinac
    TI__Guru 57321 points

    Hi,

    We are unable to duplicate your observation on the EVM. Please collect the details on the charger operation conditions before entering ship mode, activities after entering ship mode, then how users try to exit ship mode. The investigation will be resumed when more information is available.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 30 points

    Hi

    Of course, it is such an rare random issue. But if you just had any suspicions what could be the issue on my side let me know.

  • 0 in reply to Dajgoro Labinac
    TI__Guru 57321 points

    Hi,

    Maybe later when more related info is available. The thread is considered closed at the time being.

    Thanks for your understanding,

    Ning.