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BQ25890: When increase input supply current, Vbat is much over Vbattery_actually

Robin Zhou
Intellectual 625 points
Part Number: BQ25890
Other Parts Discussed in Thread: BQSTUDIO

Dear Engineers,

There is a question with BQ25890 in RK platform. when discharge, vbat reads out is 3.6v  usb_pc charging is 3.7v; When adapter 5w charging vbat is 3.9v ; 8w charging is 4.0v; 10w charging is 4.15v

Looking forward to your reply!

Thanks

Robin

  • 0
    TI__Guru 57821 points
    Robin,

    Could you please describe how the different VBAT values were obtained in more details?

    Thanks,

    Ning.
    Please click "This Resolved my issue" button if this post answer your question.
  • 0 in reply to Ning T
    Intellectual 625 points
    Ning,

    Thanks for your reply. I changed the adapters to increase supply voltage and current. Check the voltage value of the 0e register when charging at high current. Supply 5V/1A, Vbat is 3.9V; Supply 5V/1.6A, Vbat is 4.0V; Supply 12V/0.8A, Vbat is 4.15V; Supply 12V/1A, Vbat is 4.2V. However, when discharge, Vbat reads out 3.6V.

    Thanks
    Robin
  • 0 in reply to Robin Zhou
    Intellectual 625 points
    Ning,

    I use BQstudio ADC to detect Vbat. when discharge, it's 3.6V; When charging, it's more higher. Supply 5V/1A, Vbat is 3.9V; Supply 5V/1.6A, Vbat is 4.0V; Supply 12V/0.8A, Vbat is 4.15V; Supply 12V/1A, Vbat is 4.2V. However, when discharge, Vbat reads out 3.6V.
    And I also use multimeter to check Vbattery_actual.

    Or could you please help me how to detect the Vbattery_actual?

    Thanks
    Robin
  • 0 in reply to Robin Zhou
    TI__Guru 57821 points
    Robin,

    Does the device ADC reading on VBAT similar to the multimeter reading at VBAT pin?

    Thanks,

    Ning.
    Please click "This Resolved my issue" button if this post answer your question.
  • 0 in reply to Ning T
    Intellectual 625 points
    Ning,
    It's just much unsimilar.

    Thanks
    Robin
  • 0 in reply to Robin Zhou
    TI__Guru 57821 points
    Robin,

    Did you measure the battery voltage at the VBAT pin of the IC?

    Thanks,

    Ning.
    Please click "This Resolved my issue" button if this post answer your question.
  • 0 in reply to Ning T
    Intellectual 625 points
    Ning,

    The point is how I can get the actual voltage of the battery? I think REG0E is the register to read the battery voltage, but it will change with the change of the charging current.

    In addition, the current and voltage limit on the adapter seems not work. The current adapter is 5V/2A 12V/1.5A input current limit can only limit 0-1A; no matter how I adjust FAST CHARGER CURRENT LIMIT (set to 3A) input current limit (set The current of 3A)charger current can only reach 1.8A and the current of VBUS port can only reach 1A and can't rise to 1.5A; Vbus voltage input voltage limit (set to 5V) vbus is always 12V, and the input voltage limit is 8.2V. I just want increase the supply power and Icharge.

    And I wonder know how much the maximum system load is?

    Thanks
    Robin
  • 0 in reply to Robin Zhou
    TI__Guru 57821 points

    Robin,

    Referring to BQ25890 d/s page 14, the battery ADC has conversion time up to 1 second. It takes multiple measurements then does the average. For accurate ADC readings, the VBAT voltage should be constant for at least 1 second.

    BQ25890 is a 5-A charger. It can handle up to 5-A total current, i.e. the sum of the charging current and the system current.


    Thanks,

    Ning.

    Please click "This Resolved my issue" button if this post answer your question.