CS4298 Datasheet, PDF (14/52 Pages) Cirrus Logic – SoundFusion Audio/Modem Codec 97 (AMC 97)

CS4298
4. ANALOG SECTION
Please refer to Figure 8, Mixer diagram, for a high-level graphical representation of the CS4298 an-
alog mixer structure.
4.1 Audio Output Mixer
There are two output mixers on the CS4298. The stereo output mixer sums together the analog out-
puts from the Input Mixer, 3D enhancement, and the PCM DAC output. The stereo output mix is sent
to the LINE_OUT and ALT_LINE_OUT output pins of the CS4298. When the device is set to Mode
3 or Mode 0-2 and the EAM in AC Mode Control (Index 5Eh) is set, the modem DAC outputs are
routed to ALT_LINE_OUT.
4.2 Audio Input Mux
The input multiplexor controls which analog input is sent to the ADCs. The output of the input mux
is converted to stereo 18-bit digital PCM data and sent to the AMC Controller chip in Slots 3 and 4
of the AC-Link SDATA_IN signal.
4.3 Audio Input Mixer
The input mixer is an analog mix of the analog input signals such as MIC, LINE_IN, etc., and the
PCM Audio DAC output. The output of the mixer is routed to the ADC Input Mux, Audio Output
Mixer, and may be routed to the Modem ADC input.
4.4 Audio Volume Control
The volume control registers of the AC ’97 Register interface control analog input level to the input
mixer, the master volume level, and the alternate volume level. All analog volume controls imple-
ment volume steps at nominally 1.5 dB per step. The analog inputs allow a mixing range of +12 dB
of signal gain to -34.5 dB of signal attenuation. The analog output volume controls allows from 0 dB
to -94.5 dB of attenuation.
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DS315PP2