Sierra Wireless AIRPRIME WISMO218 - Manual (Page 56)

WA_DEV_W218_PTS_002 Rev 006 April 29, 2010 56
Product Technical Specification &
Customer Design Guidelines Interfaces
3.10.5.5. Audio Track and PCB Layout Recommendation
To avoid TDMA noise, it is recommended to surround the audio tracks with ground as shown in the
following figure:
Figure 22. Audio Track Design
For differential connections, it is necessary to add a 2.2KΩ resistor from MICN to GND to have a
proper bias of the microphone. Refer to the following figure.
Figure 23. Differential Audio Connection
For single-ended connections, the negative pole of the microphone, MICN, should be connected to
GND. Refer to the following figure.
Differential Audio line is
always in parallel