CS4298 datasheet(14/52 Pages) CIRRUS

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CS4298

DS315PP2

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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