User's Manual

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.
 A protection diode should be inserted close to the power input, in order to save the
GE865 from power polarity inversion. This can be the same diode as for spike protection.
An example of switching regulator with 12V input is in the below schematic: