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BQ76952: Stack voltage increases on COV

Ananya KC
Prodigy 60 points

Part Number: BQ76952

Tool/software:

This is the pack and stack voltage when there isn't any COV error. The BQ chip is in autonomous mode.

When there is a cell overvoltage error the CHG pin shows that it has been disabled but the stack voltage is higher than the pack voltage by 2 volts.

The stack voltage should be lesser than the pack voltage when the COV occurs but why is the stack voltage higher than the pack voltage? Is my understanding correct?

  • 0
    TI__Mastermind 21715 points

    Hello Ananya,

    When overvoltage is triggered, the CHG FET turns off and there will usually be a voltage drop across the body diode of the MOSFET. This voltage drop can be found in the MOSFET data sheet but it typically around 0.6V. This means that Stack Voltage is expected to be greater than PACK+. 2V does seem on the larger side. Can you double check with a DMM if the Stack Voltage and Pack Voltage measures those values as well?

    Also, have you also calibrated your Stack Voltage and Pack Voltage? If not, BQ769x2 Calibration and OTP Programming Guide can be useful.

    Best Regards,
    Alexis