Telit GE863-QUAD / GE863-PY
Hardware User guide
1vv0300715, Rev. ISSUE#0, - 21/02/06
Reproduction forbidden without Telit Communication written authorization – All Right reserved – Right of modification reserved
page 13 of 71
3.2.1.2 + 12V input Source Power Supply Design Guidelines
•
The desired output for the power supply is 3.8V, hence due to the big difference between the
input source and the desired output, a linear regulator is not suited and shall not be used. A
switching power supply will be preferable because of its better efficiency especially with the
2A peak current load represented by the GE863-QUAD/PY.
•
When using a switching regulator, a 500kHz or more 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.
•
For car PB battery the input voltage can rise up to 15,8V and this should 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 in order to cut the
current absorption peaks, a 100
μ
F 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.
•
For Car applications a spike protection diode should be inserted close to the power input, in
order to clean the supply from spikes.
•
A protection diode should be inserted close to the power input, in order to save the GE863-
QUAD/PY from power polarity inversion. This can be the same diode as for spike
protection.
An example of switching regulator with 12V input is:
