GSM/GPRS Module Series
M85 Hardware Design
M85_Hardware_Design Confidential / Released 46 / 88
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.
MICxP
Differential
layout
Module
10pF
33pF
33pF
33pF
GND
GND
Electret
Microphone
GND
GND
10pF
10pF
GND
GND
ESD
ESD
MICxN
Close to
Microphone
0603
0603
0603
0603
0603
0603
Figure 25: Reference Design for AIN1&AIN2
3.8.3. Receiver and Speaker Interface Design
SPK1P
SPK1N
Differential layout
Module
10pF
0603
Close to speaker
GND
ESD
33pF
0603
33pF
0603
GND
10pF
0603
ESD
10pF
0603
33pF
0603
Figure 26: Handset Interface Design for AOUT1