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WEBENCH® Tools/LM5145: LM5145 webench very different than excel design tool

John Moody
Prodigy 30 points
Part Number: LM5145

Tool/software: WEBENCH® Design Tools

I am designing a 3.3V 8A power supply using the LM5145. I used webench for the initial design, I noticed that Ccomp2 was very small (1.2pF)

compared to the designs in the datasheet. I entered the webench values into the LM5145 excel design tool and got totally different values for

phase margin ,etc. Who should I believe? Attached are the files.

Thanks,

John

  • 0
    TI__Mastermind 40060 points
    Hello John,

    There are a number of approaches to setting positions of zeros and poles in a type III compensator. The position of the poles and zeros are directly related to the Switching frequency/Cross over frequency, the selected Buck inductor and output capacitor, and also the ESR of the output capacitor used. I trust both will yield a stable design if followed.

    Hope this helps?

    David.