The MYBSP00502ABF and MYBSP01201ABF are PFM (frequency modulation) mode isolated DC-DC converters.
Under this control system, the oscillation frequency changes according to the load, with the oscillation frequency decreasing as the load becomes smaller.
This reduces power consumption under a light load. At the same time, because the oscillation frequency decreases to audio frequencies, this control system has the disadvantage of causing ringing to occur.
To curtail this ringing, operate the DC-DC converter with an output power of 3W or more.
When operated at 3W or more, the DC-DC converter operates at a frequency at or above the audio frequency band (20kHz).