Audio Circuit Reference; M1X; Microphone Reference Circuit - Quectel GSM Series Audio Design Manual

2.1. Audio Circuit Reference

2.1.1. M1x

2.1.1.1. Microphone Reference Circuit

M1x module provides electrets-microphone bias voltage for AIN1 and AIN2. Microphone reference circuit
is shown as below:
Module
MICxP
MICxN
Notes
1. To avoid TDD noise issue during voice, capacitors is recommended to add close to microphone and
SPK.
2. TVS components are used to protect microphone and receiver from ESD damage. It has to close to
audio device and audio interface.
GSM Module Audo Design Guide
Differential layout
Figure 1：Microphone Reference Circuit for AIN1&AIN2
GSM Module Audio Design Guide
Close to Microphone
GND
10pF ESD
33pF
10pF 33pF
ESD
10pF 33pF
GND
Confidential/Release
GSM/GPRS Modules
Electret
Microphone
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