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LM5150-Q1: Inductor Selection

Junichi Makita
Prodigy 10 points
Part Number: LM5150-Q1

Section 8.2.2.4 of the data sheet, LM(GUIDE) can be caluculated as

                                

For my application, Iload value varies depending on the load state.

In this case, is it OK for me to use ILOAD (MAX) value to obtain LM(GUIDE)?

Is there no problem expected in case when ILOAD value becomes smaller

depening on the load state?

  • 0
    TI__Mastermind 31015 points

    HI Makita-san,

    It is ok for you to use max ILoad value to obtain Lm. If you reduce Iload value, inductance will be bigger, but there will be no other issue. 

    Thanks,

    Richard

  • 0 in reply to Richard Fu22
    Prodigy 10 points

    Hi Richard,

    Thank you for your quick response.  

    May I ask one more question?

    In order to get the smaller LM(GUIDE) value, can I use the larger ILOAD value than the actual current 

    in LM(GUIDE) formula? 　 

  • 0 in reply to Junichi Makita
    TI__Mastermind 31015 points

    Hi Makita-san,

    If you use a larger value for Iload value, then that will lower the Lm(GUIDE) value- but that will still affect your Lm(target) value since Iout is higher. Lm(guide) equation is based off of the inductor's volt-second balance equation and that ΔI_L = IOUT. 

    Your inductance value that would give the best trade-off between right half plane zero, inductor ripple ratio, and inductor falling slope would be Lm(target), which is calculated through equation 20.

    Thanks,

    Richard