LE910Cx
Hardware User Guide
1VV0301298 Rev. 1.05 - 2017-06-18
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57 of 117
Figure 10 shows an example of linear regulator with 5V input.
Figure 10: Example of Linear Regulator with 5V Input
6.2.1.2.
+ 12V Input Source Power Supply – Design Guidelines
•
The desired output for the power supply is 3.8V. Due to the big difference between the
input source and the desired output, a linear regulator is unsuitable and must not be used.
A switching power supply is preferable because of its better efficiency, especially with the
2A peak current load which is expected during GSM Tx.
•
When using a switching regulator, a 500-kHz or higher 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 selection of the frequency and switching design is related to the application
to be developed due to the fact that the switching frequency can also generate EMC
interference.
•
For car batteries (lead-acid accumulators) the input voltage can rise up to 15.8V. This must
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 to cut the current
absorption peak
s. A 100μF tantalum capacitor is usually
suitable (on both VBATT and
VBATT_PA together).
•
Make sure that the low ESR capacitor on the power supply output (usually a tantalum one)
is rated at least 10V.
•
For automotive applications, a spike protection diode must be inserted close to the power
input to clean the supply of spikes.
•
A protection diode must be inserted close to the power input to protect the LE910Cx
module from power polarity inversion. This can be the same diode as for spike protection.