User Manual

GM862-QUAD / PY Hardware User Guide

1vv0300748 Rev. 5 - 20/09/07

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 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 GM862-QUAD / PY.

• When using a switching regulator, a 500Khz 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.

• A protection diode should be inserted close to the power input, in order to save the GM862-QUAD

/ PY from power polarity inversion. This can be the same diode as for spike protection.