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BQ76930: Charging and discharging problem

Xu Allen
Prodigy 20 points
Part Number: BQ76930

Tool/software:

Dears，

     The client has a product for sale in the market and has encountered a problem. Please describe it in detail:

     Product architecture:

     MCU: Domestic brand

     AFE: BQ7693003DBTR

     With Bluetooth module

     Users can detect voltage, current, temperature and MOSFET status through the Bluetooth APP.

     Fault phenomenon: The user found that charging and discharging were impossible.

     Accessing the BMS through the APP, it was found that everything was normal, and the MOS working status was also normal (this status was that the data reading was normal when connected to the BMS Bluetooth module through the Bluetooth APP, and the communication between the MCU and the BQ76930 through I2C was also normal, and the waveform was also correct. However, after our measurement, The Alert pin of BQ76930 remains at a high level all the time. The charging and discharging MOSFET is actually not turned on, meaning it cannot charge or discharge. However, the situation fed back to the MCU through I2C by BQ76930 shows that the charging and discharging are normal and can be done. All Bluetooth apps can also read data normally. If this phenomenon occurs, it will return to normal if BQ76930 is reset.

  • 0
    Prodigy 20 points

    This product use 2pcs BQ76930(U25,U26). U25 controls a high serial number of batteries, U26 controls low serial number batteries. The test situation is as follows:

    At the same time, force the alert pin of BQ76930 and keep the high and low cell battery to be raised externally for 2 seconds.

     Alert pin of U26 can automatically return to low level after 2 seconds, and the high and low levels will jump regularly.

    However, after being forcibly pulled up for 2 seconds, the alert pin of U25 does not return  and remains at a high level all the time, which causes the charging and discharging MOS to turn off and prevent charging and discharging.

    Could you please help analyze whether there are any differences in the resistors and capacitors on the alert pin of the high and low section BQ76930, or how to match the high and low section circuits?

  • 0 in reply to Xu Allen
    Prodigy 20 points

    The sch have updated as follow, please kindly help analyze it, thanks!

    3438.BQ76930 Sch.pdf

  • 0 in reply to Xu Allen
    TI__Expert 5645 points

    Hi Allen, 

    Apologies for the delay. Support queue is very high and responses are taking significantly longer than usual.

    Do you still need help on this support request? 

    Do you know if the bottom BMIC has any active ALERT on the system. The recovery from any fault even must be handled by the host MCU, such as clearing the faults and re-enabling the FETs. What's the status of the SYS_STAT on the bottom IC, U25? Keep in mind that some faults, like OV/UV may immediately re-toggle if the condition is still active. 

    Regards, 

    Arelis G. Guerrero