what is meant by low frequency noise in a DC to DC converters that the vendors claim for switching regulators? What is the frequency range?
closed as unclear what you're asking by Daniel Grillo, brhans, pipe, Bence Kaulics, Dave Tweed♦ Oct 11 '16 at 22:41
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Under light load, certain regulators can enter PFM mode which consists of varying the frequency of a pulse. If the load is light enough, the regulator will only need to supply a few (comparatively) pulses per second. This can induce low frequency noise though I'd imagine the frequency is load dependent.
The Microchip TC105 for example is a buck converter which switches between PWM and PFM mode for light load conditions - defined as duty cycles less than 10%.