Hardware Manual

 The PCB traces connecting the Switching output to the inductor and the
switching diode must be kept as short as possible by placing the inductor and the
diode very close to the power switching IC (only for switching power supply).
This is done in order to reduce the radiated field (noise) at the switching
frequency (usually 100-500 kHz).
 The use of a good common ground plane is suggested.
 The placement of the power supply on the board must be done in a way to
guarantee that the high current return paths in the ground plane are not
overlapped to any noise sensitive circuitry as the microphone amplifier/buffer or
earphone amplifier.
 The power supply input cables must be kept separately from noise sensitive lines
such as microphone/earphone cables.