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BQ24250: I2C communication issues

Part Number: BQ24250

Hi everyone,

I am issuing some problems in developing a board with the IC reported, expecially in the evaluation of the on/off charge status.

I will try to explain the flow-chart in detail, and please, let me understand if I do something wrong.

When I first start my battery powered device, everything is ok but the content of Reg5.CE_STATUS. Also when the wall adapter is disconnected, the I2C register reports a CE low status.

In sequence, during the startup of my device I do these steps:

  1. reset all the registers writing 1 to MSB in REG2.
  2. Disable the charge, by writing 1 to bit /CE in REG2.
  3. Set HI-Z Mode, disabling the charger by writing 1 on bit HZ_MODE in REG2.

After that, I see by reading again the registers their change following my expectations, but /CE_STATUS bit is again set to LOW.

Now, when I attach the power plug, there is a change in the REG1, REG5, etc, but the /CE_STATUS bit in REG5 reports again LOW.

Sometimes happens that this bit is set HIGH when detaching the power plug, but only in certain and rare conditions which I cannot reproduce.

In addiction, I wrote an if statement that: when REG1.STAT = NORMAL && REG2.CE == DISABLED && REG5_CE_status == LOW, i turn on the device by removing it from the high impedance mode and setting che enabled charge in REG2.

I am not able to revert the IC status in the initial condition, when attaching the battery for the first time.

I am attaching a short part of the schematic we have developed and the status of the registers before and after the wall-plug link.

Thank you in advice for your help.



  • Hi Andrea,

    Charge is enabled when both the /CE bit and /CE pin are low.  The /CE status register bit reports the current status of the /CE pin only.  If your /CE pin is low, then /CE status reports low.



  • Hi Jeff,

    thank you for your answer.

    This is pretty clear, the question is, why I cannot see the /CE pin bit change its value corresponding to the status of the physical pin.

    When attaching the power plug I expect to see the /CE bit LOW, and it is ok, but, when detaching the power-plug, this bit stays low and does not report a change in the hardware pin.

    By reading with a voltmeter I am sure that the pin is  @Vbat level.



  • Hi everyone,

    probably I found the solution.

    There was a porr connection between the the battery ground and the ground of the PCB.

    By replacing the battery connector the problems seems solved.

    Thank you everyone for the help.