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M20 Hardware Design
3.10.1 Microphone interface configuration
AIN1 channel has no internal bias supply for external microphone, thus an external bias circuit
must be added when connecting electret microphone to AIN1 channel. A reference circuit is
shown in Figure 24. The LDO to supply VMIC should use AGND of the module as its ground
instead of GND of the module to suppress TDD noise.
Electret
Microphone
10pF
33pF
33pF
33pF
Close to Microphone
MIC1P
MIC1N
GND
GND
Difference layout
Module
GND
GND
10pF
10pF
GND
GND
ESD
ANTI
ESD
ANTI
AGND
1K
AGND
VMIC_2V8
1K
1.5K
1.5K
10uF
Figure 24:
Electret
microphone interface configuration of AIN1
AIN2 channel comes with an internal bias supply for external microphone. A reference circuit is
shown in Figure 25.
M20_HD_V1.01
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