CS4297A
CS4297A
MONO_OUT pins require 680 pF to 1000 pF NPO
capacitors between the corresponding pin and ana-
log ground. Each analog output is DC-biased up to
the Vrefout signal reference, nominally 2.3 V. This
requires the outputs be AC-coupled to external cir-
cuitry (AC load must be greater than 10 kΩ) or DC
coupled to a buffer op-amp biased at Vrefout.
6.1.5 Phone Input
One application of the PHONE input is to interface
to the output of a modem analog front end (AFE)
device so that modem dialing signals and protocol
negotiations may be monitored through the audio
system. Figure 16 shows a design for a modem
connection where the output is fed from the
CS4297A MONO_OUT pin through a divider. The
divider ratio shown does not attenuate the signal,
6.2.1 Stereo Outputs
See Figure 18 for a line-level stereo output refer-
ence design. See Figure 17 for a recommended
headphone stereo output reference design.
providing an output voltage of 1 V
. If a lower
RMS
output voltage is desired, the resistors can be re-
placed with appropriate values, as long as the total
load on the output is kept greater than 10 kΩ. The
PHONE input is divided by 6 dB to accommodate
6.2.2 Mono Output
a line-level source of 2 V
.
RMS
The mono output, MONO_OUT, can be either a
sum of the left and right output channels, attenuat-
ed by 6 dB to prevent clipping at full scale, or the
selected Mic signal. The mono out channel can
drive the PC internal mono speaker using an appro-
6.2
Analog Outputs
The analog line-level output section provides two
stereo outputs and a mono output. The
LINE_OUT_L/R, ALT_LINE_OUT_L/R, and priate buffer circuit
TDA1308
1
2
3
-
1.0 µF
+
6.8 k
Ω
10
Ω
220 µF
ELEC
PHONE
PHONE
22 pF
NPO
HP_OUT_R
HP_OUT_L
+
+
1/4 WATT
1.0 µF
0 Ω
ALT_LINE_OUT_R
ALT_LINE_OUT_L
1
2
4
3
1
2
4
MONO_OUT
MONO_OUT
3
10
Ω
220 µF
ELEC
27
k
Ω
39
k
Ω
1000 pF
NPO
1000 pF
NPO
1/4 WATT
22 pF
NPO
4
1
3
2
6.8 k
Ω
47 kΩ
47 kΩ
6
5
1000 pF
-
AGND
7
+
VREFOUT
TDA1308
0.1 µF
Y5V
1 µF
AGND
AGND
AGND
AGND
Figure 16. Modem Connection
Figure 18. Stereo Output
39 k
Ω
22 pF
NPO
Headphone
Out
10 Ω
220
ELEC
µF
2
-
1/4 Watt
ALT_LINE_OUT_R
Vrefout
1
+
+
27 k
27 k
Ω
Ω
3
+
TDA1308
10 Ω
1/4 Watt
220
ELEC
µF
5
6
+
-
7
ALT_LINE_OUT_L
47 k
Ω
47 kΩ
22 pF
NPO
1000 pF 1000 pF
NPO NPO
39 k
Ω
AGND
AGND
Figure 17. Alternate Line Output as Headphone Output
DS318PP6
37
37
CIRRUS [ CIRRUS LOGIC ]
