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TPS54325: About IC burns on short between VIN and VBST pins on TPS54325.

Bob Lee62837
Mastermind 7230 points
Part Number: TPS54325

Dear support member,

The customer is mass producing the TPS54325.

I have a question and Urgent.
The IC burned due to a short between the VIN（13pin） and VBST（12pin) pins.

（Question)
Q1
Please tell me the mechanism by which the IC burns.


(Specification condition)
Vin: 12V
Vout: 3.3V
Iout: 1.8A

Best regard.
Bob Lee.

  • 0
    TI__Expert 8245 points

    Hi,

    Because the bootstrap circuit between VBST and SW only works below 6.5V (see Page 4 & 8 of its datasheet), if the voltage exceeds it, the device might burn. Thanks.

  • 0 in reply to Iven Su
    Mastermind 7230 points

    Dear Iven Su,

    Thank you very much for your answer.
    I understood about VBST and SW absolute max voltage.

    May I ask add a question?

    Question 2
    Could you teach the mechanism that damages the IC?
    Please describe in the internal block diagram and tell me.

    Best regard.
    Bob Lee.

  • 0 in reply to Bob Lee62837
    TI__Expert 8245 points

    Hi,

    The voltage higher than absolute max voltage will damage the low-voltage FETs which used in bootstrap circuit. Vin voltage exceeds these max drain-source voltage of these FETs, so the FETs will burn. So driver of high-side switch now is damaged and the device will not work. Thanks.

  • 0 in reply to Iven Su
    Mastermind 7230 points

    Dear Iven Su,

    Thank you very much for your answer.
    May I ask a add question about your answer?


    About Question
    （Your answer)
    So your answer that "The voltage higher than absolute max voltage will damage the low-voltage FETs which used in bootstrap circuit. "


    Question4
    Is this the low-voltage FETs a high side MOSFET?
    Is it the following high-side MOSFET?


    About Question
    （Your answer)
    So your answer that "Vin voltage exceeds these max drain-source voltage of these FETs, so the FETs will burn. "

    Question5
    Is there the absolute maximum voltage rating drain-source voltage of a High-side MOSFET?（VIN-SW absolute maximum voltage rating )?

    Is there description of datasheet?


    Because I don't understand "Vin voltage exceeds these max drain-source voltage of these FETs".


    Best regard.
    Bob Lee.

  • 0 in reply to Bob Lee62837
    TI__Expert 8245 points

    Hi,

    Answer to Q4: The MOSFET you marked out is high-side power switch, and the low-voltage FETs mentioned above are logic switches, which are basic units of control/driver circuits of the device.

    Answer to Q5: These low-voltage FETs in bootstrap circuit part have 6.5Vmax, and High-side power MOSFET is 20Vmax, thanks.

  • 0 in reply to Iven Su
    Mastermind 7230 points

    Dear Iven Su,


    Thank you very much for your answer.
    I reply my customer your answer.

    I will feedback my cusomter status.

    Best regard.
    Bob Lee.

  • 0 in reply to Bob Lee62837
    Mastermind 7230 points

    Dear Iven Su,

    Thank you very much for support.
    My customer solved.

    Best regard.
    Bob Lee.