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LMZM23600: Part fails when plugging into a power supply

Jack Kelly
Prodigy 40 points
Part Number: LMZM23600

Part fails when plugging into a power supply. The power supply is set to +24V.  The part does not fail when I turn the power supply on and off.  The part fails when I plug the the positive lead into the power supply.  When turning the power supply on and off there is no overshoot of the Vin voltage.  But when plugging the positive lead into the turned on power supply the Vin voltage will sometimes go beyond +50v.  I can sometimes see a small spark at the positive lead as I plug in. Looks like this overshoot is failing the part.  I need to clamp the Vin to less than +42V.  Any suggestion? 

  • 0
    TI__Guru 50120 points

    Hi Jack,

    If you are hot plugging the power supply, I suspect the input voltage might surge. Can you provide your schematic for review? Can you also try to add a parallel electrolytic capacitor with high ESR at the input? This capacitor should provide dampening of the input voltage so that it doesn't overvoltage the input pin of the device.

    Regards,

    Jimmy

  • 0 in reply to Jimmy Hua
    TI__Mastermind 19891 points

    Hi Jack,

    Section 10.3.2 (page 35) of the datasheet discusses adding damping bulk capacitor with sufficient ESR in order to prevent over voltage transients such as the ones you are experiencing when hot plugging the input supply. The amount of necessary ESR really depends on the inductance of the leads and the existingceramic capacitance that's already on the input of the module. The guidance in the datasheet would apply to any buck converter.

    Here is a link to the page: http://www.ti.com/lit/ds/symlink/lmzm23600.pdf#page=35

    Cheers,
    Denislav