CS4298 datasheet(39/52 Pages) CIRRUS

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CS4298

DS315PP2

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

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.

Figure 13. 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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