We are using a TPS63811 to boost an input voltage to a level were we can charge a backup battery. While the circuit is generally working correctly, we have noticed that when circuit is drawing approx. 80mA there is an audible high pitched sound. At current draw under 10mA and over about 300mA there is no audible sound. We suspect it is the inductor but we can verify that. Additionally, the frequency on the inductor at 80mA is approx 200KHz and at 5mA there a groups of pules at approx. 860Hz.
Here is the circuit schematic:
The inductor we are using is the Coilcraft XGL4030-471ME. There is also a 330uF POSCAP on the input but not shown on the schematic.
Any insight here would be helpful.
