User's Manual

LE910 Hardware User Guide

1vv0301089 Rev.3 – 09-06-2014

The principal guidelines for the Power Supply Design embrace three different design steps:

 the electrical design

 the thermal design

 the PCB layout.

The electrical design of the power supply depends strongly from the power source where this

power is drained. We will distinguish them into three categories:

 +5V input (typically PC internal regulator output)

 +12V input (typically automotive)

 Battery

 The desired output for the power supply is 3.8V, hence there’s not a big difference between

the input source and the desired output and a linear regulator can be used. A switching

power supply will not be suited because of the low drop out requirements.

 When using a linear regulator, a proper heat sink shall be provided in order to dissipate the

power generated.

 A Bypass low ESR capacitor of adequate capacity must be provided in order to cut the

current absorption peaks close to the LE910, 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.

 A protection diode should be inserted close to the power input, in order to save the LE910

from power polarity inversion.