Telit Wireless Solutions CE910-DC, Hardware User'S Manual

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The principal guidelines for the Power Supply Design embrace three different design steps:

the electrical design

the thermal design

the PCB layout
The electrical design of the power supply depends strongly on the power source where this power is
drained. We will distinguish them into three categories:

+5V input (typically PC internal regulator output)

+12V input (typically automotive)

Battery

The desired output for the power supply is 3.8V, hence there is not a big difference
between the input source and the desired output so a linear regulator can be used. A
switching power supply will not be suitable because of the low drop-out requirements.

When using a linear regulator, a proper heat sink must be provided in order to dissipate
the power generated.

A Bypass low ESR capacitor of adequate capacity must be provided in order to cut the
current absorption peaks close to the CE910. A 100μF tantalum capacitor is usually suited.

Make sure the low ESR capacitor on the power supply output (usually a tantalum one) is
rated at least 10V.

A protection diode must be inserted close to the power input in order to save the CE910
from power polarity inversion.