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BQ25895: Charge state oscillation near the end of charge

Bohdan Shubenok1
Prodigy 50 points
Part Number: BQ25895

Hi,

We are observing strange charge state indication at the end of charge. We're reading register 0B and CHRG_STAT field. And sometimes we observe oscillation between 01 (Fast charge) and 11 (Termination done) states. Period is around 2s.

Reading charge current shows 0 current and no noticable change in battery voltage.

Are we missing something here or this is expected behavior?

Regards,

Bohdan.

  • 0
    TI__Guru 57461 points

    Bohdan.

    What are your test conditions such as VBUS (voltage at VBUS pin), IVBUS, VBAT (voltage at BAT pin), IBAT, VSYS, ISYS? Could you please provide all register values of the charger?

     

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 50 points


    Hi Ning,

    Herer the registers in normal state:

    OK Reg(0x0)=0x5c
OK Reg(0x1)=0x5
OK Reg(0x2)=0x6d
OK Reg(0x3)=0x14
OK Reg(0x4)=0xf
OK Reg(0x5)=0x10
OK Reg(0x6)=0x5a
OK Reg(0x7)=0x9d
OK Reg(0x8)=0x2
OK Reg(0x9)=0x44
OK Reg(0xa)=0x93
OK Reg(0xb)=0x96
OK Reg(0xc)=0x0
OK Reg(0xd)=0x55
OK Reg(0xe)=0x5f
OK Reg(0xf)=0x5f
OK Reg(0x10)=0x47
OK Reg(0x11)=0xdd
OK Reg(0x12)=0x1
OK Reg(0x13)=0x1c
OK Reg(0x14)=0x3a

    Will share register values when will be able to reproduce issue.

    We're using MaxCharge USB charger at 12V output. USB current ussualy below 1A

    Regards,

    Bohdan.

  • 0 in reply to Bohdan Shubenok1
    TI__Guru 57461 points

    Bohdan,

    The registers look normal. Please also provide all the register vales when charge terminated.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 50 points

    Hi Ning,

    Here is the registers when cought in oscillation state:

    OK Reg(0x0)=0x5c
OK Reg(0x1)=0x5
OK Reg(0x2)=0x2d
OK Reg(0x3)=0x34
OK Reg(0x4)=0x20
OK Reg(0x5)=0x13
OK Reg(0x6)=0x82
OK Reg(0x7)=0x9d
OK Reg(0x8)=0x3
OK Reg(0x9)=0x44
OK Reg(0xa)=0x93
OK Reg(0xb)=0x96
OK Reg(0xc)=0x0
OK Reg(0xd)=0x56
OK Reg(0xe)=0x58
OK Reg(0xf)=0x59
OK Reg(0x10)=0x45
OK Reg(0x11)=0xe0
OK Reg(0x12)=0x0
OK Reg(0x13)=0x1c

    and 

    OK Reg(0x0)=0x5c
OK Reg(0x1)=0x5
OK Reg(0x2)=0x2d
OK Reg(0x3)=0x34
OK Reg(0x4)=0x20
OK Reg(0x5)=0x13
OK Reg(0x6)=0x82
OK Reg(0x7)=0x9d
OK Reg(0x8)=0x3
OK Reg(0x9)=0x44
OK Reg(0xa)=0x93
OK Reg(0xb)=0x9e
OK Reg(0xc)=0x0
OK Reg(0xd)=0x56
OK Reg(0xe)=0x58
OK Reg(0xf)=0x59
OK Reg(0x10)=0x45
OK Reg(0x11)=0xe0
OK Reg(0x12)=0x0
OK Reg(0x13)=0x1c

    Regards,

    Bohdan Shubenok.

  • 0 in reply to Bohdan Shubenok1
    Prodigy 50 points

    Hi Ning,

    Looks like BQ was reseted. We're disabling OTG by default (register 0x03) but it is set. 

    We're also disable watchdog so this may not be the reason of reset.

    Regards,

    Bohdan Shubenok.

  • 0 in reply to Bohdan Shubenok1
    TI__Guru 57461 points

    Hi,

    Multiple register values have been changed besides the OTG bit. You should disable watchdog timer by setting REG07[5:4]=00 in order to keep the desired register settings. In all your cases, REG07=9D indicates REG07[5:4]=01. Please refer to 8.3.1 Host Mode and Default Mode on the d/s for the details. Please make the change and try again.

    Thanks,

    Ning.