LE910Cx mPCIe Hardware Design Guide
1VV0301510 Rev. 13 Page 22 of 73 2021-07-07
An example of linear regulator with 5V input is:
Figure 1: An Example of Linear Regulator with 5V Input
4.3.1.2. +12V Source Power Supply Design Guidelines
• The desired output for the power supply is 3.3V, so due to the big difference
between the input source and the desired output, a linear regulator is not suitable
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 since 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 capacitor is usually suitable.
• 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 the spikes.
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