User's Manual

LE910 Hardware User Guide
1vv0301089 Rev.7 – 25-10-2015
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 37 of 88
 The PCB traces to the LE910 and the Bypass capacitor must be wide enough to
ensure no significant voltage drops occur when the 2A current peaks are absorbed.
This is for the same reason as previous point. Try to keep this trace 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 in
order to reduce the radiated field (noise) at the switching frequency (100-500 kHz
usually).
 The use of a good common ground plane is suggested.
 The placement of the power supply on the board should be done in such 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 should be kept separate from noise sensitive lines
such as microphone/earphone cables.
 The insertion of EMI filter on VBATT pins is suggested in those designs where
antenna is placed close to battery or supply lines.
A ferrite bead like Murata BLM18EG101TN1 or Taiyo Yuden P/N
FBMH1608HM101 can be used for this purpose.