User's Manual

CE910-DUAL Hardware User Guide

1vv0301010 Rev .0 – 2012-07-10

 The protection diode must be placed close to the input connector where the power

source is drained.

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

enough to ensure no voltage drops occur when the 1A current peaks are absorbed.

While a voltage drop of hundreds of mV may be acceptable from the power loss

point of view, the same voltage drop may not be acceptable from the noise point

of view. If the application does not have an audio interface but only uses the data

feature of the Telit CE910-DUAL, then this noise is not as disruptive and the

power supply layout design can be more forgiving.

 The PCB traces to CE910-DUAL and the Bypass capacitor must be wide enough

to ensure no significant voltage drops occur when the 1A current peaks are

absorbed. This is a must for the same above-mentioned reasons. 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 (usually

100-500 kHz).

 The use of a good common ground plane is suggested.

 The placement of the power supply on the board must be done in a way to

guarantee that the high current return paths in the ground plane are not

overlapped with any noise sensitive circuitry such as the microphone

amplifier/buffer or earphone amplifier.

The power supply input cables must be kept separate from noise sensitive lines such as

microphone/earphone cables.