CS4298 Datasheet, PDF (39/52 Pages) Cirrus Logic – SoundFusion Audio/Modem Codec 97 (AMC 97)

CS4298
7.4 Consumer IEC-958 Digital Interface (S/PDIF)
The CS4298 supports the industry standard IEC-958 consumer digital interface. Sometimes this stan-
dard is referred to as S/PDIF, which refers to an older version of this standard. This output provides
an interface, external to the PC, for storing digital CD-ROM) or playing digital audio from digital
speakers. Figure 14 illustrates the circuit necessary for implementation of the IEC-958 consumer in-
terface. The CS4298 is capable of directly driving the voltage divider for the 75 Ω interface. An op-
tional current driver is shown when an increase of the transmission range of the coaxial circuitry is
required. An optional fiber optic circuit may be connected directly to the CS4298.
7.5 Miscellaneous Analog Signals
The AFILT1 and AFILT2 pins must have a 1000 pF NPO capacitor (must not be smaller than 390
pF) to analog ground. These capacitors, along with an internal resistor, provide a single-pole low-
pass filter at the inputs to the ADCs. By placing these filters at the input to the ADCs, low-pass filters
at each analog input pin are not necessary.
The REFFLT pin lowers the noise of the internal voltage reference. A 1 µF (must not be greater than
1 µF) and 0.1 µF capacitor to analog ground should be connected with a short, wide trace to this pin.
No other connection should be made, as any coupling onto this pin will degrade the analog perfor-
mance of the Codec. Likewise, digital signals should be kept away from REFFLT for similar reasons.
ALT_LINE_OUT_R
ALT_LINE_OUT_L
Vrefout
1
4
2
3
27kΩ
680pF 680pF
NPO NPO
AGND
0.1µF
Y5V
1.0µF
Y5V
AGND
2_-
3₊
TDA1308
1
22pF
NPO
1
4
2
3
39kΩ
22pF
6_-
5₊
NPO
7
TDA1308
220µF
+
ELEC
220µF
+
ELEC
10Ω
1/4 WATT
10Ω
1/4 WATT
43
47KΩ
12
HP_OUT_R
HP_OUT_L
AGND
Figure 13. Headphones Driver
DS315PP2
39