• State TI Thinks Resolved
  • Locked Locked
  • Replies 15 replies
  • Answers 4 answers
  • Subscribers 63 subscribers
  • Views 220 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ25890: BQ25890 not charging when the BATV is 3.0V

Feng Xu
Intellectual 380 points
Part Number: BQ25890

When the BATV is above 3.5V,  the BQ25890 can charge the battery normally.

But when I changed another battery which has low battery (BATV is 3.0V), the BQ25890 do not charge is normally.

I read all the registers, and find that:

CHRG_STAT = 0x03, which means Charge Termination Done

NTC = BAT_COLD

TSPCT = 0x7F

But the USB current monitor shows the the USB is supplying power for my board.

I think that is because of the BATV is 3.0V which is below MINSYS(3.5V default), so the TSPCT got by the ADC is wrong. Then the BQ25890 thinks the BAT_COLD and terminate charging.

But: According to the following post, "In battery only mode, the ADC is only functional if the battery voltage is higher than the MINSYS register setting (REG03 bits1:3). "

https://e2e.ti.com/support/power-management/f/power-management-forum/585877/bq25890-sys_min-does-not-work-normally-above-3-5v?tisearch=e2e-sitesearch&keymatch=BQ25890%2525203.5V

So, in this post, it seems that even when the USB is plugged in, the TSPCT ADC still can not work normally when the BATV is below MINSYS.

Q: What can I do to make the system charging normally even when the battery has low volatage?

Below shows the configuration I set for BQ25890:

Thank you.

  • 0
    TI__Mastermind 46691 points

    Hi,

    Is there valid VBUS or not? When battery only, the battery cannot get charged.

    Thanks,

    Ning

  • 0
    Intellectual 380 points

    The VBUS is valid, and if the VBAT is above 3.5V, it can charge normally.

  • 0 in reply to Feng Xu
    TI__Mastermind 46691 points

    Hi,

    Does the 3.0V battery have built-in battery protection?

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Intellectual 380 points

    Yes, I think so. It's a common battery which is used in smartphone.

  • 0 in reply to Ning T
    Intellectual 380 points

    I think the BQ25890 stops charging because the TSPCT get NTC COLD.

    It seems that even when the USB is plugged in, the TSPCT ADC still can not work normally when the BATV is below MINSYS.

    Does BQ25890 TSPCT ADC can work normally when the BATV is below MINSYS, but the VBUS is good?

  • 0 in reply to Feng Xu
    TI__Mastermind 46691 points

    Hi,

    In battery only mode, the ADC is only functional if the battery voltage is higher than the MINSYS register setting (REG03 bits1:3). When Valid VBUS is present, it does not apply. Please measure TS pin voltage and REGN voltage then calculate the TSPCT manually. Please note that TSPCP ADC range is 21%-80% only. It can't give accurate ADC reading if TSPCT is beyond the range. Please refer to page 49 for the details.

    Thanks,

    Ning.

     

  • 0 in reply to Ning T
    Intellectual 380 points

    Hi,

         But in my case, even when the VBUS is valid, but the bq25890 is not charing the battery when the VBATT is below 3.0V.

         And with the same board, if I change a battery above 3.5V, it can charge normally

         Thanks.

    Frank

  • 0 in reply to Feng Xu
    TI__Mastermind 46691 points

    Frank,

    1. What are all register readings when not charging with VBAT<3.0V?

    2. Is there any battery protection circuitry in between BAT pin and the battery pack or does the battery have built-in battery protection? 

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Intellectual 380 points

    Hi Ning T,

          1. Some of the register readings are:

    CHRG_STAT = 0x03, which means Charge Termination Done

    NTC = BAT_COLD

    TSPCT = 0x7F

              And because the phenonmen happens occasionally, I will post all of the register readings when it happens again.

          2. Yes, there is a protection circuitry.

         

         Thank you.

    Frank

  • 0 in reply to Feng Xu
    TI__Mastermind 46691 points

    Frank,

    1. Referring to 9.2.7.5 Thermistor Qualification, If TS voltage exceeds the T1–T5 range, the controller suspends charging and waits until the battery temperature is within the T1 to T5 range. NTC cold indicates the battery temperate is below T1. Please debug and fix.

    2. The battery protection may interfere with the charger operations (e.g. disconnect the battery from the BAT pin of the charger under certain conditions). For easier debugging, it is better to connect the battery to the BAT pin of the BQ25890 directly (i.e. bypass or remove any unessential components for charging operations).

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Intellectual 380 points

    Hi, Ning

    1. The TSPCT = 0x7F 

    Yes, I think the BQ25890 stops charging because the TSPCT get NTC COLD.

    I find that, when the VBAT is above MINSYS, the TSPCT value is right. And if VBAT is below MINSYS, the TSPCT value is 0x7F even when the VBUS is good.

    That is different from "In battery only mode, the ADC is only functional if the battery voltage is higher than the MINSYS register setting (REG03 bits1:3). When Valid VBUS is present, it does not apply. "

    I will try to repeat the phenonmen and get all register values.

    Thank you.

    Frank

  • 0 in reply to Feng Xu
    TI__Mastermind 46691 points

    Frank,

    Why do you think when VBAT is below MINSYS, the TSPCT ADC reading is incorrect? Please measure VTS and VREGN at the pins, then calculate VTS/VREN=TSPCT manually and compare with the TSPCT ADC reading.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Intellectual 380 points

    When the phenonmen occurs, the register readings are:

    I will monitor the VREGN and VTS tomorrow when I get to my office.

  • 0 in reply to Ning T
    Intellectual 380 points

    Hi Ning,

         I find that the BTB interface is broken and does not connect well. And today, after I pull it off and plug it on for 2 times, it seperated from the battery.

         I think maybe this is why the battery does not charge, alrough the VCC and GND is connected, maybe the VTS signal pin of the BTB interface is not well connected with the battery, and maybe even shorted with VCC.

         I will change a new BTB and try.

         Thank you.

    Frank

  • 0 in reply to Feng Xu
    TI__Mastermind 46691 points

    Frank,

    Thanks for the update. The thread is considered closed. Please start a new thread if there's any new questions.

    Ning.