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LMR51430: How does the PFM version works in light load？

Zoe Yang
Intellectual 2210 points
Part Number: LMR51430

Hi team,

How does the PFM version works in light load? In customer system, they use two pieces LMR51430. One Vin=24V, Vout=5V,Iout=200mA. The other one is Vin=5V Vout=3.3V Iout=20mA.

The capture shows the blue channel is 24V-->5V's 5V output, the yellow channel is 3.3V output from the second channel. Why the waveform is like that in blue channel?

  • 0
    TI__Guru 50120 points

    Hello,

    Please let me know what the waveform in both blue channel and yellow channel are.

    1. Is it SW or inductor current? 
    2. How is the waveform being measured? Are you hovering the probe around any noisy circuit or inductor which can capacitively couple SW to probe?
    3. Do you have a schematic I can review for both circuits?

    Information about PFM configuration in light load are detailed in the datasheet below:

    Regards,

    Jimmy