User's Guide

LE920A4 HW User Guide Power Supply
Doc#: 1VV0301261 General Design Rules
Rev. 4.7.1 Page 61 of 124 2019-11-21
For this reason, while a voltage drop of 300-400 mV may be acceptable from the
power loss point of view, the same voltage drop may not be acceptable from the
noise point of view. If your application does not have audio interface but only uses
the data feature of the module, this noise is not so disturbing, and the power
supply layout design can be more forgiving.
 The PCB traces to the module and to the bypass capacitor must be wide enough
to ensure that no significant voltage drops occur when the 2A current peaks are
absorbed. This is needed for the same above-mentioned reasons. Try to keep
these traces as short as possible.
 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 to
reduce the radiated field (noise) at the switching frequency (usually 100-500 kHz).
 Use a good common ground plane.
 Place the power supply on the board in a way to guarantee that the high current
return paths in the ground plane do not overlap any noise-sensitive circuitry, such
as the microphone amplifier/buffer or earphone amplifier.
 The power supply input cables must be kept separate from noise-sensitive lines,
such as microphone/earphone cables.