User's Manual

GL865 Hardware User Guide

1vv0300910 Rev.1 – 2011-07-22

page 26 of 79

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 GL865.

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.