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BQ76200: BQ76200 with an additional mosfet

Frank Xiao
Genius 12055 points
Part Number: BQ76200
Other Parts Discussed in Thread: BQ78350, , BQ76930

Hi team,

 

My customer is using BQ78350+BQ76930+BQ76200 now, and meets one problem.

For 6 series Li battery with one BQ76200, the customer also uses a 16v TVS in parallel with the 100Mohm resistor.

 

For two battery package series application, they use the low side PACK+ connect with high side PACK-, and High side PACK+ as the +, the low side PACK- as the -.

For this condition, once short the circuit(pack+ connect pack-) and open one battery. The BQ76200 DSG cannot stand the -24v. It will make the device and mosfet fail.

From the datasheet, the min voltage is -0,3v, the DSG internal may have a 100V TVS.

Can we add one mosfet like BQ76930 below to solve the problem?

 

Thank you.

  • 0
    TI__Guru 54715 points

    Hi Frank,

    Modular batteries where each module has independent protection switches have the challenges of high voltage or reverse voltage when the protection FETs open.  The bq76200 simple schematic does not support negative voltages on the PACK+.  The application note bq76200 Reverse Voltage Considerations describes the issue and shows an example circuit. The circuit for your specific implementation should address several items:

    • Keep the discharge FET off
    • Switch off the gate and source paths (DSG and PACK pins)
    • Protect the IC pins

    Since the signal switch may not be perfect, the system should anticipate the leakage when protected and accomodate the long term effect.