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BQ25723: We use an adapter as MB's power,and when the adapter is not completely powered off, power it back on and the charger has no VSYS output.

段 璇
Prodigy 50 points
Part Number: BQ25723
Other Parts Discussed in Thread: BQ24725

Tool/software:

Using an 19V adapter to power the MB without connecting the battery,when the adapter is turned off and its output voltage drops to around 3.6V, the charger's VSYS has no output but the LDO output is normal when the adapter is power back on.

Another issue is that when the input voltage of BQ25723 drops,the Vsys voltage starts to decrease after only dropping by less than 2V, as the picture shows blow.

  • 0
    TI__Mastermind 33275 points

    Out of office today. Will get back to you next week.

  • 0 in reply to Tiger Zhou
    Prodigy 50 points

    Dear zhou,

    I need to find the reason of this problem as soon as possible.If you need our schematic for analysis,please let me know.

  • 0 in reply to 段 璇
    TI__Mastermind 33275 points

    Hi, Duan,

    1. When the input voltage is lost, the BQ25723 will report a STAT_VDPM fault. You will need to clear this bit to restart. Alternatively, when the input voltage drops below 3.25V, it will trigger a system restart. So, if you wait until the VBUS below 3.25V, you will see a POR and the system restart. Or, you can send a command to clear the STAT_VDPM fault and force the system to restart. 

    2. The default VINDPM level is VBUS-1.28V.  When the VBUS drops below VINDPM, without battery support, the system voltage will collapse and trigger STAT_VDPM fault. You can set VINDPM =3.2V to have a wide input operating range. Set REG 0X0A =0. 

    I hope this helps. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    Prodigy 50 points

    Hi,Tiger,

    Thanks for your answer.And we use an EC to control the charger now, how can we clear the STAT_VDPM fault? Please tell me the specific command.Besides,when we used elder IC such as B24725 before,there was no such problem. I want to know that why there is such a feature in current design.

    Regards,

    Duan

  • 0 in reply to 段 璇
    TI__Mastermind 33275 points

    Hi, Duan,

    Just write STAT_VDPM=0 to reset the fault. We consider adapter removal / input collapse a severe condition which needs EC attention. BQ24725 is a different family, which might not have this feature. 

    Regards,

    Tiger