User's Manual

GE865 Hardware User Guide

1vv0300799 Rev.11 – 13-07-2010

An example of linear regulator with 5V input is:

6.3.1.2 + 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

shall not be used. A switching power supply will be preferable because of its better

efficiency especially with the 2A peak current load represented by the GE865.

When using a switching regulator, a 500kHz 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 should 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.

Make sure the low ESR capacitor on the power supply output (usually a tantalum one)

is rated at least 10V.

For Car applications a spike protection diode should be inserted close to the power

input, in order to clean the supply from spikes.