Manual
CS4299-BQ
38
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. Figure16 shows a design for a modem
connection where the output is fed from the
CS4299-BQ MONO_OUT pin through a divider.
The divider ratio shown does not attenuate the sig-
nal, providing an output voltage of 1 V
RMS
. If a
lower output voltage is desired, the resistors can be
replaced with appropriate values, as long as the to-
tal load on the output is kept greater than 10 kΩ.
The PHONE input is divided by 6 dB to accommo-
date a line-level source of 2 V
RMS
.
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
MONO_OUT pins require 680pF to 1000pF NPO
capacitors between the corresponding pin and ana-
log ground. Each analog output is DC-biased up to
the Vrefout signal reference, nominally 2.3V. This
requires the outputs be AC-coupled to external cir-
cuitry (AC load must be greater than 10kΩ) or DC
coupled to a buffer op-amp biased at Vrefout.
6.2.1 Stereo Outputs
See Figure18 for a line-level stereo output refer-
ence design. See Figure17 for a recommended
headphone stereo output reference design.
6.2.2 Mono Output
The mono output, MONO_OUT, can be either a
sum of the left and right output channels, attenuat-
ed by 6dB 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-
priate buffer circuit
PHONE
MONO_OUT
PHONE
MONO_OUT
6.8 k
Ω
1.0
µ
F
0 Ω
6.8 k
Ω
1.0
µ
F
47 k
Ω
AGND AGND
1000 pF
Figure 16. Modem Connection
ALT_LINE_OUT_R
ALT_LINE_OUT_L
27 k
Ω
1000 pF
NPO
AGND
3
2
1
220
µ
F
ELEC
220
µ
F
ELEC
+
+
1000 pF
NPO
27 k
Ω
47 k
Ω
AGND
22 pF
NPO
39 k
Ω
5
6
7
22 pF
NPO
39 k
Ω
+
-
+
-
TDA1308
Vrefout
10 Ω
1/4
Watt
10 Ω
1/4
Watt
47 k
Ω
Headphone
Out
Figure 17. Alternate Line Output as Headphone Output
AGND
ALT_LINE_OUT_R
27 k
Ω
1000 pF
NPO
1000 p F
NPO
1
2 3
4
AGND
0.1 µ F
Y5V
220 µ F
+
5
-
39 k
Ω
1
2 3
4
+
3
-
22 pF
NPO
22 pF
NPO
6
2
7
1
TDA1308
TDA1308
ALT_LINE_OUT_L
VREFOUT
+
ELEC 1/4 WATT
10
Ω
HP_OUT_R
220 µ F
+
ELEC 1/4 WATT
10
Ω
HP_OUT_L
47 k
Ω
1
34
AGND
2
1 µF
Figure 18. Stereo Output
38 DS319-BQPP2
CS4299-BQ