Integra M2106+
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This document is the sole and exclusive property of Wavecom. Not to be distributed or divulged without prior written
agreement.
WA_DE_PTS_003-001
April, 2007
3.9
Audio Interface
Two different microphone inputs (MIC1 and MIC2 inputs) and two different speaker outputs (SPK1 and SPK2
outputs) are supported.
The connection can be either differential or single-ended but the use of a differential connection in order to
reject common mode noise and TDMA noise is strongly recommended. When a single-ended connection is
used, ensure to have a good ground plane, good filtering as well as shielding, in order to avoid any
disturbance on the audio path.
The Integra Wireless CPU
®
also includes an echo cancellation feature, which allows hands-free function.
In some cases, ESD protection must be added on the audio interface lines.
3.9.1
Microphone Inputs
The MIC2 inputs already include the biasing for an electret microphone allowing easy connection to a
handset.
The MIC1 inputs do not include an internal bias. MIC1 is appropriate for a hands-free system, headset or car
kit. However, MIC1 can also be used for a handset with external biasing.
3.9.1.1
Common Microphone Input Characteristics
Both microphone inputs are designed with the following audio transmit characteristics:
Internal audio filter characteristics
Frequency
Gain
0-150 Hz
< -22 dB
150-180 Hz
< -11 dB
180-200 Hz
< -3 dB
200-3700 Hz
0 dB
> 4000 Hz
< -60 dB
The gains in the MIC inputs are internally adjusted and can be tuned from -6.5dB to 51.3dB by using AT
commands. Two different gain ranges (controller1 and controller2) are available and can be selected with AT
command software (refer to the AT commands Interface Guide documentation [7] for details).
The two microphone inputs are composed of a 1
st
order high pass filter with a cut-off frequency of 330Hz.
