WM_PRJ_Q2400_PTS_005 -007
18th January 2006
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Linear regulation (recommended) or PWM (Pulse Width Modulation) converter
(usable) are preferred for low noise.
PFM (Power Frequency Modulation) or PSM (Phase Shift Modulation) systems
must be avoided.
2.1.3 PCB routing constraints
2.1.3.1 Power supply routing Constraints
•
A ground plane must be provided on the PCB. This plane must not be
parcelled out.
•
Attention shall be paid to the power supply tracks and to the ground plane
which supply the module. The tracks and the plane used must support
current peaks.
•
Since the maximum peak current can reach 2 A, Wavecom strongly
recommends a large width for the layout of the power supply signal (to
avoid voltage loss between the external power supply and the module
supply. Filtering capacitors, near the module power supply, could also be
added (refer to section 2.1.3.3).
•
The routing must be done in such a way that the total impedance line
must be
≤
10 m
Ω
@ 217 Hz. This impedance must include the via
impedances.
•
Same care shall be taken when routing the ground supply.
•
If these design rules are not followed, phase error (peak) and power loss
could occur.
2.1.3.2 Application ground plane and shielding connection
The grounding connection is done through the shielding
the four legs have to
be soldered to the ground plane (
see Wavecom recommendation for lead free
soldering in Section 5.3).
A ground plane must be available on the application board to provide efficient
connection to the WISMO module shielding.
Best shielding performance will be achieved if the application ground plane is a
complete layer of the application PCB:
•
To ensure a good shielding of the module, a complete ground plane layer
must be available, with no trade-off. Connections between other ground
planes shall be done with vias.
•
Without this ground plane, external Tx spurious or Rx blockings could
appear.
It is strongly recommended to avoid routing any signals under the module.
