Hello All....
I am looking for some general insight / things to try to dampen some low amplitude audio that emanates from a power supply design using the above subject....The design is a 3.3V, PFM design. I am driving a 15 foot cable that feeds a sensor.....It is a very low power application so PFM seems to be the way here....I have done some extensive testing / plotting and the audio frequency is directly related to the switching frequency which of course is related to the load current....There are a few sweet spots where the amplitude does change which implies to me that I probably have a mechanical resonance in those regions.....Overall the level is quite low. I am more interested as I will re-spin the PCB on things I can do to potentially eliminate or dampen the noise......I have a very tight design with respect to space......The switcher drives five 47uF, 1210 package capacitors then that feeds (through a diode OR) a bank of four 100uF 1210 package capacitors....All ceramic, X7S or X7R. The inductor is a 68uH wirewound shielded core....
Thanks
Steve
