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Does LM3224 do pulse skipping?

Borge Strand-Bergesen
Intellectual 695 points
Other Parts Discussed in Thread: LM3224

I'm bringing up a prototype where an LM3224 delivers 8mV in a 5V->8V configuration. When I scope the SW pin it looks like a square-ish pattern intersected with a sine-ish pattern. The stated 24MHz SRF of the inductor is at a much higher frequency than this sine-like pattern.


As far as I can see, the datasheet doesn't say anything about the LM3224 performing pulse skipping when the current is low. Do you know if this is the case?

Or could this be the onset of inductor self resonance at short current pulses? If so, would it help to lower or increase the inductor SRF?

Both images show SW on the top and the 8V output on the bottom. Both are AC coupled. The onset of sine-ish patterns on SW correlates with a drop in output voltage, as may be expected from pulse skipping. However, the board still shows switching behaviour, so I don't quite understand what is going on.

Thanks,

Børge