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LM5148: LM5148

Yu-cheng Yeh
Prodigy 30 points

Part Number: LM5148
Other Parts Discussed in Thread: LM25148

Tool/software:

Hi TI

The datasheet of LM5148 table 9.1 shown the common formula to maeuserd MOSFET'S power loss

But the spreadsheet of  "LM5148_LM25148_quickstart_calculator_A4" didnt use these parameters.

for exsample, the formula of MOS's "switching loss" mention the Tr & Tf as MOSFET's parameter.

this parameter is typical method.

how can i measure it?

When I used webench to simulate, the webench recommended the MOS and the simulation results to illustrate the loss of MOS.

I tried to fill in the MOS parameters recommended by webench into the spreadsheet.
The results of the spreadsheet do not match the results of the webench simulation.

how can i measure it?

  • 0
    TI__Guru* 90027 points

    Hello,

    The MOSFET switching times are calculated internally in the quickstart file. It's effectively the rise/fall time of the SW voltage and current, which is related to the Qgd and gm of the high-side MOSFET, respectively.

    Regards,

    Tim

  • 0 in reply to Timothy Hegarty
    Prodigy 20 points

    Hi Tim

    My question is how to solve the problem that the formula does not match the result of the spreadsheet?
    For example, the result of the spreadsheet shown the curve of power loss.
    But the results obtained by the formula in the datasheet are not consistent.

    The datasheet recommends the formula Tr/Tf for calculation, but the spreadsheet does not. As you mentioned, the spreadsheet uses Qgd and GM for calculations, however, the results are different.

    It seems that the spreadsheet calculation results in MOS cannot be used.

  • 0 in reply to Yu-cheng Yeh
    TI__Guru* 90027 points

    Hi Yu-cheng,

    The quickstart uses the expressions in the datasheet. Please send your quickstart file for review.

    Regards,

    Tim