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LM5117: Fsw changes when load is heavier

Jerry Chen
Expert 5110 points
Part Number: LM5117

Hi,

               I observed an issue on LM5117. Input is 24V, output is 5V, fsw=240kHz. When I increased the load from 5A to 10A, I found the fsw is changed to 120kHz. The output remained 5V. It didn't look like OCP. For this ECM controller, what is the probable cause to make the fsw changed? Could you pls show me any idea?

Thanks.

  • 0
    TI__Mastermind 39980 points
    Hello Jerry,

    It looks like the Fsw/2 is really sub harmonic osculation, please refer to the datasheet regarding slope compensation and the k factor of the amount of slope you are adding in the current loop as it relates to the inductor current. I suggest increase Vslope by either decreasing Rramp or decreasing Cramp. Suggest a k of 1.5 to 2, to check if issue goes away?

    Hope this helps?

    David.