LG KU950 Service Manual page 61

3. TECHNICAL BRIEF
3.10.10.2. 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. Detailed diagram of MSM6275 audio interface
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