NL865B1 HW Design Guide
1VV0301450 Rev. 1
Page
25
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72
2017-11-20
4.3.1.2.
+12V 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.
•
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 c
urrent absorption peaks, a 100μF capacitor is usually suited.
•
Make sure the low ESR capacitor on the power supply output 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.
An example of switching regulator with 12V input is in the below schematic:
