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BQ25703A: Clarification on charger behavior

VENKATAPPA SACHIN
Intellectual 350 points
Part Number: BQ25703A

1) On disconnect of TypeC hub, system shutdowns abruptly

During disconnect of TypeC hub from system, we are programming ChargeVoltage (Register 05/04h) and ChargeCurrent (Register 03/02h) to '0'.
Writing '0' leading to abrupt system power off.

During system bring-up, we are programming 6000mAH in ChargeCurrent and 8400mV in ChargeVoltage register.

Please clarify why writing to 0 leading to system power off.

2) CHGR_OK/AC_STAT is high in but not charging

CHGR_OK/AC_STAT is high in ChargerStatus (21/20h) register but Charging not happening (Bit1 and Bit2 are zero in 21h register).

Under what circumstances, Charger will not charge even though CHGR_OK high.

Register dump:
Reg04 = D0
Reg05 = 20
Reg02 = 40
Reg03 = 17
Reg32 = 37
Reg33 = 02
Reg0E = 00
Reg0F = 1D
Reg00 = 20
Reg01 = 82
Reg20 = 00
Reg21 = A0

Thanks.

  • 0
    TI__Expert 3320 points

    Hi there:

         For 1), It is little hard for me understand why system is off, what is the battery voltage before setting charge voltage/current to 0?  As long as battery exist the system voltage should be hold up by the battery because BATFET body diode. If battery is low, then Reg 0D/0C should be effective to hold system voltage higher than minimum system voltage. Please include VBUS/VSYS/VBAT and Reg0D/0C setting before setting ICHRG and VCHRG to 0 for more analysis. 
        

         For 2), Couple things hope you to check:


                     1,If Pin6 is pulled down to below 0.4V.

                     2,Please make sure R35<7>=0 to disable HIZ.

                     3,Would you please check Reg21/20 to see if there is any fault triggered. 

                     4, Please also include the VBUS, VBAT and VSYS information for more analysis.

         

  • 0 in reply to Shishuo Zhao
    Intellectual 350 points

    Thanks for response.

    For 1) After debug we found that charge voltage/current writing to '0' is not causing issue. Our software is writing 0 in IIN_HOST(0E/0F) register during disconnect of TypeC charger from TypeC port. If don't write 0 in IIN_HOST register then no issue.

    In MinSysReg (0D/0C) programming 7168mV.

    During charger plug, software programs 3A where as during charger unplug software program 0A. Please clarify why writing 0 in II_HOST causing this issue.

    Thanks.

  • 0 in reply to VENKATAPPA SACHIN
    TI__Expert 3320 points

    Hi There:
        

         How many load is adding to the system when this unplug happens? What is the battery voltage at this time? Please provide these information for further analysis.

         For above #2, I notice the R21=A0 which means VAP is enabled. In VAP mode, battery is not able to charge for sure. I think we need to disable VAP mode by setting REG34[5]=0. And pull low VAP/OTG pin.

    Regards

  • 0 in reply to Shishuo Zhao
    Intellectual 350 points

    Thanks Zhao for response.

    For #2 I see bit5 in REG34 is Reserved. And as per my register dump:

    REG[34] = 0

    REG[35] = 0

     Please clarify. 

  • 0 in reply to VENKATAPPA SACHIN
    TI__Mastermind 25800 points

    Hey Venkatppa,

    When you write the IIN_HOST() register to 0mA, the charger will attempt to regulate the input source current to 0mA. In reality, this is not a real scenario. Any minor current flowing through the input will force the charger to reduce the output power (including the SYS voltage) in order to regulate the input current to 0mA.

    I recommend not setting to 0mA.

    Regards,

    Joel H