+12V Source Power Supply Design Guidelines
• The desired output for the power supply is 3.8V, so due to the large 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.
• A regulator must be provided to absorb current peaks. The recommended
switching regulator is 500kHz or more. Due to its smaller inductor size and faster
transient response, it has a higher switching frequency.
• The frequency and selection of Switching design are related to the application,
since the switching frequency could also generate EMC interferences.
• For a PB car battery the input voltage may rise up to 15,8V and this must be
considered when selecting components: all components in the power supply must
support this voltage.
• A low ESR Bypass capacitor must be included to stop the current absorption peaks
near the Module. The recommended capacitor is 100μF.
• Make sure the low ESR capacitor on the output of the power supply is rated at least
10V.
• For Car applications, a spike protection diode should be placed close to the power
input, to clean the supply from the spikes.
Figure 3: An example of switching regulator with 12V input
Battery Source Power Supply Design Guidelines
The nominal output of the desired power supply is 3.8V and the maximum voltage allowed
is 4.2V. So a single 3.7V Li-Ion cell battery type is sufficient to power the Telit ME910G1
module.
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