Telit Wireless Solutions HE910-EU V2, 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 HE910 V2. 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
HE910 V2 from power polarity inversion.