User's Manual

GE864- QUAD Har dwar e User Guide

1vv0300872 Rev.1 2010-04-02

The protection diode must be placed close to the input connector wher e

the power source is dr ained.

The PCB traces from the input connector to the power regulator IC must

be wide enough to ensure no voltage drops occur when the 2A current

peaks are absorbed. Note that this is not made in order to save power

loss but especially to avoid the voltage drops on the power line at the

curr ent peaks frequency of 216 Hz that will reflect on all the components

connected to that supply, introducing the noise floor at the burst base

frequency. For this reason while a voltage drop of 300-400 mV may be

acceptable from the power loss point of view, the same voltage drop may

not be acceptable fr om the noise point of view. If your application does not

have audio inter face but only uses the data feature of the Telit GE864-

QUAD, then this noise is not so disturbing and power supply layout design

can be more for giving.

The PCB traces to the GE864-QUAD and the Bypass capacitor must be

wide enough to ensure no significant voltage drops occur when the 2A

curr ent peaks are absorbed. This is for the same reason as previous

point. Try to keep this trace as short as possible.

The PCB traces connecting the Switching output to the inductor and the

switching diode must be kept as short as possible by placing the inductor

and the diode very close to the power switching IC (only for switching

power supply). This is done in order to reduce the radiated field (noise) at

the switching frequency (100-500 kHz usually).

The use of a good common ground plane is suggested.

The placement of the power supply on the board must be done in such a

way to guarantee that the high cur rent return paths in the gr ound plane

are not overlapped to any noise sensitive circuitry as the microphone

amplifier/buffer or earphone amplifier .

The power supply input cables must be kept separ ate fr om noise sensitive

lines such as microphone/earphone cables.