LG KU730 Service Manual page 61

3. TECHNICAL BRIEF
3.11.10.2. Audio Signal Processing & Interface
The MSM6275 device integrates a wideband audio CODEC into the mobile station modem. The
wideband codec allows the MSM device to support stereo music/ringer Melody applications in addition
to the 8 kHz voice band applications on the forward link. In the audio transmit path, the device
operates as 13-bit linear converter with software selectable 8 kHz and 16 kHz sampling rate. In the
audio receive path, the device operates as a software selectable 13-bit or 16-bit linear converter with
software selectable 8 kHz, 16 kHz, 22.05 kHz, 24 kHz, 32 kHz, 44.1 kHz, or 48 kHz sampling rate.
Through software, the Rx path can be configured as either a mono or stereo output.
The integrated CODEC contains all of the required conversion and amplification stages for the audio
front end. The CODEC operates as a 13-bit linear CODEC with the transmit (Tx) and receive (Rx)
filters designed to meet ITU-T G.712 requirements. The CODEC includes a programmable sidetone
path for summing a portion of the Tx audio into the Rx path. An on-chip Voltage/Current reference is
provided to generate the precise voltages and currents required by the CODEC. The on-chip voltage
reference also provides a microphone bias voltage required for electret condenser microphones
typically used in handset applications. The MICBIAS output pin is designed to provide 1.8 Volts DC
while delivering as much as 1 mA of current. Audio decoder summing and headset switch detection
are included. The CODEC interface includes the amplification stages for both the microphone and
earphone. The interface supports two differential microphone inputs and a differential auxiliary input,
each of which can be configured as single-ended if desired. In addition, the interface supports one
differential earphone output, one single-ended earphone output, and one differential auxiliary output or
two single-ended line outputs. The CODEC is configured through the QDSP4000 command types and
is not directly controlled by the microprocessor. The CODEC configuration command is sent to the
QDSP4000 and then the QDSP4000 executes the command and configures the CODEC. Data is
exchanged between the codec interface and the QDSP4000 through its DMA interface. The
QDSP4000 uses the Ex_DMA_4 channel for reading data from the codec and uses the Ex_DMA_5
channel to transfer data to the codec. The CODEC interface is shown in more detail in Figure below.
Figure. Audio Interface Detailed Diagram(MSM6275)
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