User guide

UC864-E/G/WD/WDU Hardware User Guide
1vv0300766a Rev.4
- 03/02/09
Reproduction forbidden without Telit Communications S.p.A’s. written authorization - All Rights Reserved. Page 25 of 78
5.2.1.1. + 5V Input Source Power Supply Design Guidelines
• 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 and a linear
regulator can be used. A switching power supply will not be suited
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 UC864-E/G/WD/WDU,
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 UC864-E/G/WD/WDU from power polarity inversion.