Integration Guide

Routing Constraints and Recommendations
Rev 1.0 Nov 19 11 41113538
Note: Figure 4-1 shows separate traces for VBAT_BB and VBAT_RF. If VBAT_BB and
VBAT_RF share a single power supply, these traces should be connected.
Note: For optimal decoupling, place the capacitors on the underside of the board, directly
under the pins.
• Filtering capacitors (100 nF to 1500 μF) are recommended near the module’s
power supply.
• Attention should be paid to the ground trace or the ground plane on the appli-
cation board for the power supply that supplies the module. The ground trace
or ground plane, as well as the VBAT trace, must be able to support current
peaks.
• If the ground trace between the module and the power supply is a copper
plane, make sure it is a solid plane.
• Design routing to make sure total line impedance does not exceed
10 mΩ @ 217 Hz.
Ground Plane Connection
The AirPrime WP7611 requires a solid, central ground plane (with solder mask
defined pads) located directly under the module. This will:
• Ensure high current signal returns
• Provide heat dissipation under higher operating temperatures
The ground plane should be connected (with vias) to the reference ground layer
of the application board.
UIM Interface
• The length of the tracks between the AirPrime WP7611 and the UIM socket
should be as short as possible. Maximum recommended length is 10cm.
• ESD protection is mandatory on the UIM lines unless there is no physical
access to the UIM.
• The decoupling capacitor(s) should be placed as close as possible to the UIM
card connector for the UIM1_VCC signal.
RF Circuit
The RF signal must be routed on the application board using tracks with a 50Ω
characteristic impedance.
The characteristic impedance depends on the dielectric, the track width and the
ground plane spacing.
It is recommended to use stripline design if the RF path is fairly long (more than
3 cm), since microstrip design is not shielded. Consequently, the RF (transmit)
signal may interfere with neighboring electronic circuits. In the same way, the
neighboring electronics (micro-controllers, etc.) may interfere with the RF
(receive) signal and degrade the reception performance.