xE70-915 RF Module User Guide
1VV0301106
rev.3 – 2015-03-04
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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
1µH
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
