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LM5118: SNVS566J

Tahsin Sönmez
Prodigy 10 points
Part Number: LM5118

Hello,

I am designing a converter with LM5118. In this process, I follow the typical application in the datasheet. However, I noticed some errors in the calculations and I would like to both report and confirm them.

The first error is the Iripple (buck) calculation on page 27. It is calculated as 3.36 in the datasheet, but I calculate the result as 2.86. The second is the k (buck) calculation on page 28, calculated as 1.16 in the datasheet, but I calculated it as 1.33.


In addition, how big can we choose the k value to keep R(sense) at the desired value, can there be a problem of exceeding the upper limit? 

Thank you very much in advance.

  • 0
    TI__Mastermind 19540 points

    Hi Tahsin,

    Thanks for using the e2e forum.
    The calculation within the datasheet look okay to me, so I am confused that the results are different.

    I would need some additional time to check if the results in the datasheet have been calculated based on different equations, or if we put in the wrong values into the formula. (Just from some quick calculations, I do get different results as well).

    I can strongly recommend our Power Stage Designer tool in such a case. This tool helps in inductance selection and also shows ripple and peak current graphs when double clicking on the inductor within the schematic.
    https://www.ti.com/tool/POWERSTAGE-DESIGNER

    Feel free to use this tool to double check our design.

    For the second question, if the sense resistance is too large, the overcurrent protection will be triggered even during normal operation.

    To avoid this, please select a sense resistor that is small enough to support the expected peak inductor current without triggering a fault.

    Best regards,
    Niklas