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LMR16030: The inductance affects the SW waveform

user5883945
Expert 1806 points
Part Number: LMR16030

Dears,

   Customer found that the inductance affected the SW output waveform, which made the output abnormal. Does inductance affect the SW waveform? What is the cause

The first inductance is TDK SLF10165T-100M3R8-3PF, it make SW waveform abnormal as the fig1;

                                      Fig1

Change the inductance to another supplier for same parameter, the SW waveform is normal as fig 2;

Fig 2

The two inductance datasheet as attachment, sch as fig 3;

SLF10165.pdf

PS1038-103N.pdf

  • 0
    TI__Mastermind 35210 points

    Hi,

    Inductance impacts the peak to peak ripple current. A lower inductance causes the peak to peak ripple current increase.

    The device's inductor current goes discountinous (due to no reverse current through D9) when the inductor current is negative.

    This is more likely to occur at lighter loads, or when the inductance is lower.

    If there is a tolerance on the inductor, perhaps in fig1 the inductance is lower causing discontinuous inductor current as shown in the sw waveform where it resonates. 

  • 0 in reply to Marshall_Beck
    Expert 1806 points

    Hi，

      I see the fig1 inductor TDK SLF10165T-100M3R8-3PF tolerance is lower than another.

  • 0 in reply to user5883945
    TI__Mastermind 35210 points

    Hi,

    There may be an unaccounted variable between the two experiments.

    In any case, if you would like to vary my claim of the inductor current going negative, please provide A-B comparison of the inductor current waveform to see if one goes discontinuous and the other does not. The SW waveform is pretty evident that the inductor current is going discontinous.