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LMR51430: Minimum Inductor selection

Part Number: LMR51430

LMR51430 support,

I went through the equations in section 9.2.2.4 of the datasheet, and the value for the inductor selection is different from the result given in the datasheet.  It looks like the calculation is based on a Vin Max of 12 V rather than 36 V, even though it should be 36 V according to the Design Example Parameters.

Please let me know the correct way to handle this calculation.

Thanks,

Darren

  • Hi Darren, 

    The calculation is correct assuming the value of Vin used is the nominal value of 12V listed in the Design Example Parameters. When calculating the inductor, you can consider smaller or larger values of inductance. Smaller inductors will have less DCR, faster transient response, and a smaller solution size. However, too small of an inductance can cause the inductor ripple to become too large. If the ripple is too large, then an overcurrent response may be falsely triggered.

    Using the nominal voltage should cover most conditions with the above advantages. However, designing for the maximum voltage will better ensure that the device can supply the load across the input voltage range.

    Best regards,

    Ridge Lahti