cs4297 Cirrus Logic, Inc., cs4297 Datasheet - Page 31

• Manufacturer Part Number: cs4297
• Description: Crystalclear Soundfusion Audio Codec 97 Logic
• Manufacturer: Cirrus Logic, Inc.

DS242F5
(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 V
Line Level Outputs
The analog output section provides a stereo line-
level output and an alternate stereo line-level out-
put.
ALT_LINE_OUT_L, and ALT_LINE_OUT_R
outputs should be capacitively coupled to external
circuitry.
CS4297
CrystalClear™ SoundFusion™ Audio Codec ’97
Vrefout
ALT_LINE_OUT_R
ALT_LINE_OUT_L
1
AGND - if CMOS Source
LINE_OUT_L,
+5VA (Low Noise) or
2.7 nF
47 k
RMS
Figure 7. Mono Input
.
4.7 k
Y5V
0.1 F
0.1 F
680pF
NPO
AGND
AGND
680pF
NPO
PC_BEEP
1
2
1.0 F
Y5V
LINE_OUT_R,
27k
Figure 8. Headphones Driver
4
3
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
k ) or DC coupled to a buffer op-amp biased at the
Vrefout voltage (see Figure 8 for the recommended
headphone op-amp circuit).
2
3
1
2
6
5
-
+
-
+
22pF
NPO
22pF
NPO
TDA1308
TDA1308
39k
4
3
1
7
ELEC
220 F
220 F
ELEC
+
+
AGND
4
1 2
3
1/4 WATT
1/4 WATT
47K
10
10
HP_OUT_R
HP_OUT_L
31