Neo_M660A GPRS Module Hardware User Guide
Copyright © Neoway Technology Co., Ltd
23
3.7
Audio Interface
Table 3-7
Audio interface
Pin Name
I/O
Function
Remarks
MICP
AI
Positive electrode of MIC output
Vpp≤200 mV
MICN
AI
Negative electrode of MIC output
RECP
AO
Positive electrode of receiver output
32Ω receiver driving output
RECN
AO
Negative electrode of receiver output
M660A supports two lines of audio interfaces. You can switch the audio channels and adjust the volume via
AT commands. For details, see
Neo_M660A GPRS AT Command Set
.
Figure 3-22 shows a reference audio interface design. The peak voltage routed to MICP/MICN should not
exceed 200 mV AC. AGC circuit is integrated inside the module. Electret microphone is suited.
The module can meet the requirements of common handsets with AGC and volume control.
Figure 3-22
Reference design of MIC differential connections
GPRS Module
33 pF
MIC
33 pF
100 pF
MICN
MICP
In Figure 3-23, a bias voltage for microphone is provided through MICP and MICN. But if an amplifier is
used between the microphone and module, capacitors like C1 and C2, should be placed between the outputs
of amplifier and module, to block the bias voltage.
For a peak voltage greater than 200 mV AC, an attenuation circuit comprised of R1-R4 should be used.
