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BQ25820: ACDRV stopped working and REGN lost voltage output

eichi hirose
Prodigy 10 points

Part Number: BQ25820
Other Parts Discussed in Thread: , BQ24610

Tool/software:

I created a board based on the BQ25820EVM.

It worked at first, but then ACDRV stopped working and REGN lost voltage output.

I think the surge voltage from the power input was applied to the VAC and damaged the BD25820.

Is that correct?

I've attached a part of the schematic.

Please tell me a good solution.

  • 0
    TI__Mastermind 39481 points

    Hello Eichi,

    Are you able to communicate with the IC?

    Have you replaced the IC?

    Why is there two inputs?

    Best Regards,

    Christian

  • 0 in reply to Christian Moyer
    Prodigy 10 points

    Hello Christian,

    Thanks for the reply

    >Are you able to communicate with the IC?

    I don't have an I2C connection, so I can't check the communication with the BQ25820.

    >Have you replaced the IC?

    BQ25820 has not been replaced yet.

    >Why is there two inputs?

    This is to connect two types of power supplies.

    The power supply voltage VIN when operating was 48V.

    I checked further.
    The resistance between BQ25820 ACDRV (pin 31) and GND was about 10kΩ.
    A normal product was over MΩ.

    Please tell me a good solution.

  • 0 in reply to eichi hirose
    TI__Mastermind 39481 points

    Hello Eichi,

     

    Do you know how high the surge voltage was? The device should be able to handle up to 85V before getting damage.

    I recommend replacing the IC to see if it was damaged.

    Best Regards,

    Christian

  • 0 in reply to Christian Moyer
    Prodigy 10 points

    Hello Christian, Thanks for the reply

    I know the maximum ratings for the BQ25820 from the datasheet.

    However, it is unclear how much surge voltage was applied to the VAC.

    Also, Q1 and Q2 on the BQ25820EVM appear to be damaged.

    Judging from the way it broke, I think the BQ25820 and the FET broke due to overvoltage, not overcurrent.

    ・The FETs used on our board are the same as those used in the BQ25820EVM (VDS: 80V).We'll try replacing the FET with one that has a higher VDS.

    ・We've previously used the BQ24610. Looking at the circuit diagram in the datasheet for this IC, we can see that there is a low-pass filter (10 Ω, 1 uF) before VCC.

    ・We'll also review the TVS diode (currently: SMAJ58A).

    Based on this idea, we will try to think of ways to suppress the surge voltage applied to the IC and FET.