Modes Of Operation; Sidetone Support - Sierra Wireless MC5725 Hardware Integration Manual

MIC_P
MIC_N
Audio In
RF Filter
33n
22p
35mW @ +3dBm0
SPK_N
SPK_P
Audio Out
Rev 1.9.1 Feb.09
In the event of a discrepancy in values between this guide and the Product Specification Document (PSD), the PSD takes precedence.
Note: Data mixing is not supported. If mixing of voice signal is
required, it must be done by the host processor.
Figure 4-3: MC8775V / MC8785V / MC8790V / MC8791V / MC8792V Audio system block
57.3mVrms
@ 0dBm0
13 bit A/D
MIC_AMP1_GAIN
-6dB to +49.5dB
in 1.5dB steps
AMP_SEL
001 010 100
13 bit D/A

Modes of operation

These modules support four operational modes: headset,
handset, car kit, and speakerphone—end products can use any
combination of these modes.
The host device must use host‐modem messaging to tell the
module which mode to use for each call.

Sidetone support

The sidetone path mixes the near‐end transmit voice to the
near‐end receive. This gives the near‐end user some feedback
that indicates that the call is up and that the audio system is
functioning.
The sidetone path can be enabled in either the PDA codec or
the Mini Card modem—each path is equally valid. It should
not be added to both devices, and for speakerphone or car kit
applications, both sidetone paths should be disabled.
The typical handset sidetone is 12 dB below transmit voice
levels.
Proprietary and Confidential
PCM Audio interface
TX ADC Encoder
TX_HPF_DIS_N
TX_SLOPE_FILT_DIS_N
CodecTxGain
HPF &
Slope
+12dB
0dB
-84dB
CodecSTGain
+12dB
-48dB
-96dB
CodecRxGain
RX_HPF_DIS_N
HPF
+12dB
0dB
-81dB
RX DAC
Audio Interface
+12dB
-3dB
-84dB
nsSwitch TxPCMFilt TxVolume
NS &
Tx FIR
13K CELP/
AAGC
EVRC
Encoder
DTMF Tx Gain
DTMF DTMF
Decoder Encoder
Decoder
DTMF Rx Gain
13K CELP/
Rx FIR AAGC EVRC
Decoder
RxVolume
+12dB
RxPCMFilt
-25dB
-84dB
RF
Interface
55