User Manual

GSM/GPRS Module Series
GC10 Hardware Design
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cases, DCS1800 TDD noise is more obvious. Therefore, you can have a choice based on test results.
Sometimes, even no RF filtering capacitor is required.
The capacitor which is used for filtering out RF noise should be close to audio interface. Audio alignment
should be as short as possible.
In order to decrease radio or other signal interference, the position of RF antenna should be kept away
from audio interface and audio alignment. Power alignment and audio alignment should not be parallel,
and power alignment should be far away from audio alignment.
The differential audio traces have to be placed according to the differential signal layout rule.
3.8.2. Microphone Interfaces Design
AIN1 and AIN2 channels come with internal bias supply for external electret microphone. A reference
circuit is shown in the following figure.
Figure 26: Reference Design for AIN1&AIN2
The ESD protection components on the MIC channels are strongly recommended.
NOTE