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LM5175 Buck Boost quick start tool and Rsense

Robert Ploeg
Prodigy 240 points
Other Parts Discussed in Thread: LM5175

I am designing an application with the LM5175 following input: 11V - 24V dc and settable output 14V@12A or 19V@8A output.

In the example, SNVSA37A, the output is set to 12V@6A and input of 6-36V. I am using that as a basis for the calculations for Rfb1, Rfb2, L and Rsense.

In the Buck Boost quick start tool, the values of Rfb1 and Rfb2 are swapped compared to the calculation. What is correct?

Also using the formula in the datasheet to calculate the power dissipation on Rsense, 3mOhm, gives me just over 4W (Psense=(170m/3m)^2*3m*(1-11/19), where the quick start tool gives 0.6W at the 11V in and 19V out.

Are the formulas wrong or is the quick start tool wrong?

Thanks.

Rob

  • 0
    TI__Genius 11490 points

    Hi Robert,

    The RFB1, 2 in datasheet refers to the schematic in the datasheet. Those in the quick-start refer to the schematic in the quickstart. When the correct schematic is referenced they are both correct.

    The datasheet RSENSE power dissipation equation is for current limit.

    The quick-start RSENSE power dissipation is for full load.

    Thanks and regards,
    Vijay