User's Guide

HE863 Family Hardware User Guide
1vv0300891 Rev.5
- 2011-03-18
Reproduction forbidden without Telit Communications S.p.A’s. written authorization - All Rights
Reserved. Page 41 of 89
An example of linear regulator with 5V input is:
6.2.1.2. +12V Input Source Power Supply Design Guidelines
 The desired output for the power supply is 3.8V, hence
due to the big difference between the input source and
the desired output, a linear regulator is not suited
and must not be used. A switching power supply will be
preferable because of its better efficiency especially
with the 2A peak current load represented by HE863
Family.
 When using a switching regulator, a 500 kHz or more
switching frequency regulator is preferable because of
its smaller inductor size and its faster transient
response. This allows the regulator to respond quickly
to the current peaks absorption.
 In any case, the frequency and Switching design
selection is related to the application to be
developed due to the fact the switching frequency
could also generate EMC interferences.
 For car PB battery the input voltage can rise up to
15.8V and this must be kept in mind when choosing
components: all components in the power supply must
withstand this voltage.
 A Bypass low ESR capacitor of adequate capacity must
be provided in order to cut the current absorption
peaks. A 100μF tantalum capacitor is usually suited
for this.