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BQ77915: Schematic review for LFP 4S protection board with fast turn off feature for Short circuit protection

Gopal Pipil
Prodigy 10 points
Part Number: BQ77915

Tool/software:

4S15Amps BMS.pdf

Hi TI,

We are developing a protection board for LFP 12.8V30Ah battery with BQ7791514PWR IC and We need to ensure that the schematic is designed correctly. Kindly check if everything is okay here.

We are planning to have a fast response time during the short circuit and fly back diode to protect MOSFET during short circuit and reverse polarity.

  • 0
    TI__Mastermind 36640 points

    Hello Gopal,

    For the MOSFET circuitry, I would suggest to copy the EVM values.

    For the BJT turn-off circuit, I would recommend that you add a resistor to it, at least a 0-Ohm as a place holder. You have to be careful to not turn-off the MOSFET too fast, that can cause a large positive voltage transient on the traces/battery itself, due their inductances.

    Best Regards,

    Luis Hernandez Salomon

  • 0 in reply to Luis H. S.
    Prodigy 10 points

    Hi Luis, 

    Are you suggesting adding a resistance to the emitter of the BJT?

    Apart from these, is everything else all right?

  • +1 in reply to Gopal Pipil
    TI__Mastermind 36640 points

    Hello Gopal,

    On the collector of the BJT. As is, the turn-off could be too fast and cause issues.

    For the other components around, I would suggest to follow EVM values.

    Best Regards,

    Luis Hernández Salomon