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LM5121: questions of LM5121

Jimmy Lai
Expert 6845 points
Part Number: LM5121


Dear Team,

Customer do the short circuit test, M3 will be damaged.

We design the retry time is 12mS. Cres use 0.33uF. But gate retry signal is 240uS.

Do you have any recommend? Thanks !

Many Thanks,

Jimmy

  • 0
    TI__Mastermind 19715 points

    Hello Jimmy,

    Thanks for reaching out to us via e2e.

    I would think that we see the inrush current limitation followed by the first overcurrent detection on that screenshot.
    But I do not have enough information about the setup and timing.

    Can you please provide more information about which time of the process is shown in that screenshot.
    Has the short been applied before or after the input power?
    Can you show a more zoomed-out scenario?

    The datasheet sates:
    Soft turn-on is achieved by slowly turning on the disconnection switch
    Therefore the FET will often be operated in the ohmic region.

    A FET must be chosen that can handle this mode without overheating.
    A switching FET will not work for this purpose.

    Also, please follow these other instruction for the choice of the FET which are listed in section
    8.2.2.18 Disconnect Switch QD Selection

    Lastly, please also add the filter resistors and capacitor in the current sense line as shown in the schematic, Figure 39.


    Best regards,
    Harry

  • +1 in reply to Harry Hofner
    TI__Guru 67555 points

    Hello Jimmy,

    As we did not hear back from you, I expect that the answer was sufficient or you solved your issue yourself. I will close this thread now. If my assumption is wrong, please post below or create a new thread, if this one is already locked.

    Best regards,
    Brigitte