LE910Cx Hardware Design Guide
1VV0301298 Rev.40 Page 57 of 149 2023-03-16
Not Subject to NDA
6.3.1. Electrical Design Guidelines
The electrical design of the power supply strongly depends on the power source where
this power is drained. Power sources can be divided into three categories:
+5V input (typically PC internal regulator output)
+12V input (typically automotive)
Battery
6.3.1.1. + 5V Input Source Power Supply – Design Guidelines
The desired output for the power supply is 3.8V. So, the difference between the input
source and the desired output is not great and therefore a linear regulator can be used.
When using a linear regulator, a proper heat sink must be provided to dissipate the
generated power.
A switching power supply is preferred to reduce power consumption.
In case you decide to adopt a switching regulator, we suggest selecting a synchronous
type, despite the little increase in price, you will enjoy many advantages (you don’t need
the external diode, the EMC design is generally easier, the efficiency rises from typ.
82% to typ. 93%, the switching frequency will be much higher thus allowing
smaller/cheaper inductor and output filter and presenting a lower output impedance)
When the power supply output impedance is not low enough to prevent voltage drops
during absorption peaks a low ESR by-pass capacitor of adequate capacity is
recommended. A 100 μF capacitor is usually suitable on both VBATT and VBATT_PA
power lines (check that this value of output capacitor is within the acceptable range of
the voltage regulator you decided to use).
Make sure that the low ESR capacitor on the power supply output is rated at least 10V.
In case a polarity inversion is not prevented in other way, a protection diode placed near
the power input could help to protect the LE910Cx module.
Figure 14 shows an example of a linear regulator with 5V input.
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