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LM5141: ripple current equation in datasheet

Cedrick
Expert 8270 points
Part Number: LM5141
Other Parts Discussed in Thread: LM25141

Hi,

Good day.

Our customer is using the LM5141 and they have the following question.

" I believe there is an error in the LM5141 datasheet (and also in LM25141).  Equation (13) on page 19 and Equation (15) on page 24 both state the inductor selection criteria with respect to ripple current.  However, this equation seems to be missing the duty cycle term, i.e. (1-Vout/Vin) that should be multiplied with the first term of the equation.  This leads to inductors that are significantly oversized.  Can you check into this and see if I have read this correctly?  Or is there something else to this that requires such a large inductance, regardless of duty cycle.?"

I hope you could help us on this matter. Thank you.


Regards,

Cedrick

  • 0
    TI__Guru* 75882 points

    Hi Cedrick,

    That's correct. The inductor should generally be sized for 30-40% ripple current, and this aligns with the internal slope compensation. Please use the quickstart calculator to assist with component selection as that uses the correct equation.

    Regards,

    Tim