User's Manual

HiLo3G-850 User Manual
04 March 2011 - Page 33 / 36
 Data bus and commands have to be routed on the same layer, none of the lines of the bus shall be parallel to other lines
 Lines crossing shall be perpendicular
Suitable other signals track width, thickness.
Data bus must be protected by upper and lower ground plans
8.1.5 Radio
 Provide a 50 Ohm micro strip line for antenna connection
8.1.6 Audio
Differential signals have to be routed together, parallel (for example HSET_P/HSET_N).
Audio signals have to be isolated, by pair, from all the other signals (ground all around each pair).
Cancel any loops between VBAT and GND next to the speaker to avoid the TDMA burst noise in the speaker during a
communication.
Figure 32: Layout of audio differential signals on a layer n
Figure 33: Adjacent layers of audio differential signals
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.