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BQ77915: DSG MOS FET don't open after UV condition recover

Yue TANG
Expert 8695 points
Other Parts Discussed in Thread: BQ77915

art Number: BQ77915

Hi experts,

My customer met a urgent problem during BQ77915  PP test, Need some suggestions here to help to locate this issue. schematic is as attached.  This is a 15 series cells scenarios.  3 pcs BQ77915 stack, As they described, they used a instrument to simulate UV of battery to to test each cells,[Down to 2.9V to trigger the UV, and recover from 3.3v], the cell of  6~15  is OK, but when tested 1~5, the DSG MOSFET can't recover from this UV condition. 

They tried to increase the resistance of LD pin(14 pin) to 10M, it  recovered from this problem, but this made the load removal detection insensitive.

Please suggest what may keep the DSG FET off even the UV condition disappear. thanks.  also, please suggest if we have a example to show how to stack 3pcs BQ77915? thanks.

  • 0
    TI__Guru* 81034 points

    Hi Yue,

    Figure 26 in the datasheet shows the current path through the resistors that may explain what is happening to cause this behavior. They appear to be using a smaller gate resistor for the CHG FET. The datasheet recommends a higher value of 3.3M to ensure proper load removal detection. If they need a smaller resistor on the CHG gate for faster turn-off, then they will need to raise the value of the LD pin resistor. 

    Maybe they should try 3.3M on the LD pin resistor to see if it resolves the issue.

    Best regards,

    Matt