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LM5122: Highside and lowside MOSFET damage

Zhang Liang
Genius 3450 points
Part Number: LM5122

Tool/software:

Hi,

We use the LM5122 for the BOOST circuit, and now the highside MOSFET and Lowside MOSFET are both damaged, please kinldy review the waveform and schematic diagram and provide your commend that is there any error for our design, thanks. 

The schematic diagram:

The waveform:

The MOSFET spec.

  • 0
    TI__Mastermind 26330 points

    Hi Zhang,

    Thanks for using the e2e forum.
    The output target voltage is set to 48V, correct?
    Can you also provide the input voltage and the maximum load conditions?

    Based on these parameters it is easier to review the design.

    One thing I can already say that the current limit is set to 18.87A based on the chosen sense resistance.
    The inductor shows a saturation current limit of 15A, so it is possible it saturates before the overcurrent protection triggers, which can lead to strong current spikes that my damage the FETs.


    Thanks and best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    Genius 3450 points

    Hi Niklas,

    Thanks for your circuit analysis, and based on your commend, we need to choose the larger continuous current of the inductor,

    and the current is more than 20A, right?

  • 0 in reply to Zhang Liang
    TI__Genius 17215 points

    Hi Liang,

    Yes, choose an inductor with saturation current higher than 18.87A.

    And what is the test condition when the damage happened? Please share more waveforms.

    Best Regards,

    Feng