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Original question:

BQ76952: Communication between STM32 and Bq76952 fails.

BQ76952: bq76952 has no CUV protection

jmyang
Expert 1186 points
Part Number: BQ76952

TI experts,

                4 battery samples,There is a battery without CUV protection.

                Please refer to the attached GG file and charge and discharge data.

                As you can see from the GG file,CUV=2.83V; shutdown =2.80V.

                Why is there no CUV protection action?

No CUV protection 76952-0-36-10bei-0.143mR-R00-2022-1-26.gg.csv

 

No CUV protection-0301#-0.5C-CHG-0.2C-DSG-2022-2-16.zip

   

  • 0
    TI__Guru* 81034 points

    Hi JM,

    Looking at the log file, it does look like the DSG FET is turning off around the time the CUV threshold is crossed. The log file is not showing all of the registers though and there are several seconds between readings, so it is difficult to see everything. Can you log the Safety Alert registers and the Alarm Status registers? Is it possible your microcontroller is clearing the CUV fault? Did you do any calibration on the cell voltage gains? This would affect the reported cell voltage readings.

    Regards,

    Matt

  • 0 in reply to Matt Sunna
    Expert 1186 points

    Hi Matt,

    I increased the CUV voltage from 2.83 to 2.89V while reducing the shutdown voltage from 2.8V to 2.75V.

    That is, the distance between the CUV voltage and the shutdown voltage is widened.
    Then the problem disappeared.
    What is your comment?

  • 0 in reply to jmyang
    TI__Mastermind 42060 points

    Hello Jmyang,

    I noticed that your CUV delay time is really large, at ~50 seconds. The device went from the CUV voltage to the SHUTDOWN voltage in just 16 seconds according to the log file, so there wasn't enough time for the CUV protection to trigger before SHUTDOWN took over. The delay for SHUTDOWN is 60s, according to your log the device went into shutdown exactly 60 seconds after it reached the SHUTDOWN voltage.

    You could lower the CUV delay time so it protects the voltage before it reaches SHUTDOWN. However, I would also recommend you widen the SHUTDOWN voltage gap (as you've already done). A battery pack ideally should never go into SHUTDOWN unless it is critical to do so.

    Best Regards,

    Luis Hernandez Salomon