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LMR51440: OCP point

user6544449
Intellectual 795 points
Part Number: LMR51440

Hello Team,

Recently, my customer use lmr51440 to design an 24V to 12V/4A power, and now the OCP point is 3.9A, What factors led to this result?

The L: 5.6uH, Frequency: 931Khz,

Here is a schemetic.

Thanks!

  • +1
    TI__Genius 14125 points

    Hello,

    The chosen inductor is not properly rated for this application. The LMR51440 is a 4A buck converter with a high side current limit of 7.5A maximum (refer to Section 7 of the datasheet). The chosen inductor has a saturation current rating of 3.7A, which is less than the 4A rating of the buck converter and significantly less than the high side current limit. The inductor is likely saturating, which is not over-current protection.

    For the device to function properly in an over-current event, the inductor needs to have a saturation current rating greater than the maximum high side current limit listed in the datasheet. Choosing a properly rated inductor is important to prevent the inductor from saturating during normal operation and during an over-current event. If the inductor saturates, the device will not be able to function properly. 

    Best regards,

    Ridge