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Theory of Operation
MIC
SEL
Internal
MIC
01
MIC
AMP1
Headset
10
MIC
External
11
MIC
MIC_AMP1_GAIN
00 - 2dB
01 +6dB
10 +8dB
11 +16dB
A/D converter & Filtering
Tx Volume Control
Headset Microphone Path
External Microphone Path
2003
external
components
(0dB~- 96dB)
MIC
AMP2
13bit
Digital
A/D
filtering
MIC AMP2
Sidetone to
BYPASS
Output Path
A/D is 13-bit linear two's complement converter. MIC AMP1
and MIC AMP2 gains should be selected to maximize the
dynamic range without overloading the A/D (3.63Vpp max
range). The transmit data from the microphone input is
digitally filtered with an ITU G.712 compliant filter. The filter
attenuates the input signals outside the 3400 Hz baseband and
decimates the data rate to 8 kHz. The MSM6050 has two
optional digital filters on the Tx path prior to the Vocoder, a
slope filter and a high-pass filter. The slope filter is designed to
provide pre-emphasis for the high frequency audio prior to the
Vocoder.
The Tx and Rx audio path have separate volume controls to adjust the
loudness levels on the Tx and Rx audio paths. The Rx and Tx volume
controls are programmable multipliers
The Headset Microphone is pin 4 of EAR200, which is a 2.5mm jack.
MICBIAS 1.8V from MSM is used for headset Mic bias. The single-
ended MIC2P signal is fed to MSM headset Mic input and this line is
shared as headset SEND/END detect signal from headset.
The External Microphone input is connected to pin 16 of CN300
(AUDIO_IN), the accessory connector for the mobile phone. The path
is routed through IC301 to protect ESD and to the AUXIP pin on
MSM. This single-ended signal feeds directly to the input MIC select
multiplexer without an intervening gain stage. The audio signal shall
have a nominal level (-27dBv) of 43.5mVrms at 1 kHz, between 300
Hz and 3 kHz.
Motorola Confidential Proprietary
Codec
Tx Gain
nsSwitch
ESEC
NS &
TX FIR
or
AAGC
AEC
DTMF_TX_GAIN
DTMF
Detection
MSM6050
V810
Tx Volume
EVRC
13K CELP
DFM
DTMF
Generation
AUDIO
Loopback
Page 23
TX
Interface
Packet/DFM
Loopback
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