User's Manual

Note d‘étude / Technical document :
URD1– OTL 5696.1– 003 / 72361 Edition 02
HILO 3G Application Note
17 January 2011 - Page 35 / 38
8.1.7 Shielding
A few shielding comments are provided for designer consideration:
At least the following devices and circuits should be shielded:
• High-speed memory
• RF front-end components
• Crystal circuits
• DC/DC circuits
• RF circuitry
Recommended shield partitioning:
• RF matching components, do not locate matching inductors too close to shield walls (this may cause electromagnetic
coupling and inductor de-Q).
• Memory devices must be shielded.
• The crystal circuits (other than the reference for RF frequency synthesizers) must be very close to their corresponding
pins.
• Metalized plastic is not as effective as metal cans.
• Shielded inductors might be needed in the DC/DC circuits, or they might need to be placed in their own shield area.
8.2 Example of layout for customer’s board
The following figure shows an example of layer allocation for a 6- layers circuit (for reference only):
Depending on the customer‘s design the layout could also be done using 4 layers.
Figure 34: Reference 6 layers PCB stack