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bq24105 won't go back to battery detection mode when battery removed

Kevin Lin
Expert 1445 points
Other Parts Discussed in Thread: BQ24105, BQ24125

Hi there,

I am facing an issue that bq24105 will not go back to detection mode when the battery is removed at voltage between 3.7V and 4V.  However, when battery voltage is at 3.3V or when the battery is fully charged, the charger will go back to the battery detection mode.  

Since some batteries are without a NTC, I have a NTC on board for those batteries, and I have simplified the application by removing extra circuit but the issue still remains.  Is there anything inappropriate in the design?

thank you 

By the way, what is the difference between bq24105 and bq24125?  They look identical from their datasheet.

Regards,

Kevin 

  • 0
    TI__Mastermind 20570 points

    Can you share scope capture on the insertion and removal of the battery? Please probe the battery voltage as close to the BAT pin as possible.

    The functionality of the device is the same except the bq24125 has enhanced EMI performance.

  • 0 in reply to Jing Zou
    Expert 1445 points

    Hi Jing,

    Here is the waveform when inserting/removing the battery.   Please let me know if there is anything I need to change in the circuit.  Thank you

    Battery Insertion:

    Battery removal:

    regards,

    Kevin

  • 0 in reply to Kevin Lin
    TI__Mastermind 20570 points
    Can you please upload your schematic with higher resolution? The one you uploaded in your previous post is not clear.

    When the battery is removed, the output signal goes up due to the stored energy in the inductor.Looks like for some reason the voltage at BAT is held at 4.4V. Can you also plot the output current? IDISCHARGE applies after the output current goes to 0.
  • 0 in reply to Jing Zou
    Expert 1445 points

    Hi Jing,

    Thank you for your help.
    I have solved the issue. It turned out that MOSFET we used to control the current for batteries without a NTC was the cause when it was off.

    thank you

    regards,

    Kevin