CS4297 datasheet(31/46 Pages) CIRRUS

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DS242F5

CS4297

CrystalClear™ SoundFusion™ Audio Codec ’97

(AFE) chip so that Modem dialing signals and pro-

tocol negotiations may be monitored through the

audio system. Like all other analog inputs, this pin

must be AC coupled and the input signal must be

limited to 1 VRMS.

Line Level Outputs

The analog output section provides a stereo line-

level output and an alternate stereo line-level out-

put.

LINE_OUT_L,

LINE_OUT_R,

ALT_LINE_OUT_L, and ALT_LINE_OUT_R

outputs should be capacitively coupled to external

circuitry.

The mono output, MONO_OUT, can be used as ei-

ther a sum of the left and right output channels at-

tenuated by 6 dB to prevent clipping at full scale or

the selected MIC_IN signal. The mono out channel

can be used to drive the PC internal mono speaker

using an appropriate drive circuit. This approach

allows the traditional PC sounds to be integrated

with the rest of the audio system. The mute control

is independent of the line outputs allowing the

mono channel to mute the speaker without muting

the line outputs.

Each of the 5 analog outputs, if used in the design,

require 680 pF or larger NPO dielectric capacitors

between the corresponding pin and AGND. Each

analog output is DC biased up to the Vrefout volt-

age signal reference which is nominally 2.2 V. This

requires that the output either be AC coupled to ex-

ternal circuitry (AC load must be greater than 10

Ω) or DC coupled to a buffer op-amp biased at the

Vrefout voltage (see Figure 8 for the recommended

headphone op-amp circuit).

2.7 nF

47 k

Ω

4.7 k

Ω

0.1

µF

PC_BEEP

+5VA (Low Noise) or

AGND - if CMOS Source

Figure 7. Mono Input

Figure 8. Headphones Driver

AGND

1/4 WATT

HP_OUT_R

ALT_LINE_OUT_L

HP_OUT_L

Vrefout

ALT_LINE_OUT_R

22pF

NPO

39k

Ω

22pF

NPO

TDA1308

27k

Ω

TDA1308

220

µF

ELEC

47K

Ω

1 2

ELEC

680pF

NPO

680pF

NPO

0.1

µF

Y5V

1.0

µF

Y5V

220

µF

Ω

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