User's Manual

xE70-915 RF Module User Guide
1VV0301106 rev.3 – 2015-03-04
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights
Reserved. Page 26 of 34
6. Board Mounting Recommendation
6.1. Electrical environment
The best performances of the xE70-915 module are obtained in a “noise free” environment.
Some basic recommendations must be followed:
Noisy electronic components (serial RS232, DC-DC Converter, Display, Ram, bus,...)
must be placed as far as possible from the xE70-915 module.
CAUTION – A particular attention must be put on power supply DC-DC converter, due to
switching frequency that generates spurious into the receiver band. It can strongly decrease
module performances. Therefore it is recommended to put a metallic shield covering DC
conversion function.
Switching components circuits (especially RS-232/TTL interface circuit power
supply) must be decoupled with a 100 µF low ESR tantalum capacitor. The
decoupling capacitor must be placed as close as possible to the noisy chip.
6.2. Power supply decoupling on xE70-915 module
The power supply of xE70-915 module must be nearby decoupled. A LC filter is strongly
recommended in case of DC-DC conversion. It must be placed as close as possible to the
radio module power supply pin, VDD.
For example:
Symbols Reference Value Manufacturer
L1
LQH32CN1R0M33
H Murata
C1 GRM31CF51A226ZE01 22µF Murata
C2 Ceramic CMS 25V 100nF Multiple
L1 must be chosen carefully with very low serial resistance (ESR) in order to limit voltage drop.
V
dd
C1 C2
Power Supply
L1