Earphone Interface Design - Quectel M85 User Manual

SPK2P
Module
AGND
Figure 29: Speaker Interface Design with an Amplifier for AOUT2
The suitable differential audio amplifier can be chosen from the Texas Instrument's website
(http://www.ti.com/). There are other excellent audio amplifier vendors in the market too.
NOTE
4.
The value of C1 and C2 here depends on the input impedance of audio amplifier.

3.8.4. Earphone Interface Design

MIC2N
MIC2P
Module
SPK2P
AGND
M85_Hardware_Design
Differential layout
C1
C2
Differential
layout
22uF
AGND
Figure 30: Earphone Interface Design
Confidential / Released
GSM/GPRS Module Series
Close to Speaker
Amplifier
10pF
0603
circuit
10pF
0603
Close to Socket
GND
4.7uF
10pF
33pF
0603
0603
68R
10pF
33pF
ESD
0603
0603
GND
M85 Hardware Design
GND
33pF
ESD
0603
33pF ESD
0603
GND
ESD
3
4
2
1
AGND
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