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BQ78350-R1: BQ78350-R1+BQ76940+BQ76200

lx luo
Prodigy 130 points
Part Number: BQ78350-R1
Other Parts Discussed in Thread: BQ78350, BQ76200, BQ76940,

Tool/software:

FAE， Hello!
I have made a 14S lithium battery protection board using BQ78350-R1+BQ76940+BQ76200. Currently, I have produced 15pcs of samples, but 4pcs of them are NG. The phenomenon is PF-SUV raising the flag. When testing BQ76940 PIN44-ALERT, the voltage changes from 0V to 3.3V every few seconds. However, when reading the voltage of CELL 1-14 from BQ78350, it does not meet the SUV conditions. Can you help me analyze the reason for this? The schematic diagram and test phenomenon diagram are shown below.
Thank you.

  • 0
    TI__Guru 56716 points

    The gauge doesn't use a single point measurement like what you show for SUV. If PF Status SUV is set then one or more cell voltages fell below the thresholds that you configured for the required time that you configured in the past. It won't clear automatically if voltages recover as you show in this screenshot.

  • 0 in reply to Dominik Hartl11
    Prodigy 130 points

    ,Hello!

    Are you saying that the IC detects a voltage lower than the SUV threshold at the beginning of power on?
    However, by issuing commands in sequence for testing, the SOV and SUV registers have been configured with the longest delay, and it can be found that SUV appear repeatedly:
    1. PF-EN → SUV logo still present;
    2. PF_CLEAR → SUV disappears, CHG/DSG FLAG=0, Still unable to charge or discharge;
    3. PF-EN → SUV reappears;

    Thanks!

  • 0 in reply to lx luo
    TI__Guru 56716 points

    Please check if this also happens when you apply a voltage to cell 15.

    The gauge runs a simple threshold comparison in the protection loop so if it sets the SUV PF one or more voltages that it checked were below the UV threshold. I can only go by your screenshots and your description and the only voltage that is for sure below the threshold is cell voltage 15 (0V).

  • 0 in reply to Dominik Hartl11
    Prodigy 130 points

    Dominik Hartl11, Hello!

    I uploaded the GG file, can you help me check if there is a configuration issue? In theory, the Cell has been configured for 14S, and even if the voltage at the 15S is 0V, it should not trigger the PF state, right？

    Thanks!

    BLEJ.gg.csv