Microphone Interfaces Design; Receiver And Speaker Interface Design - Quectel M85 User Manual

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
Module
MICxN

3.8.3. Receiver and Speaker Interface Design

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