CS8415A-CS datasheet(36/42 Pages) CIRRUS

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CS8415A

14. APPENDIX A: EXTERNAL

AES3/SPDIF/IEC60958 RECEIVER

COMPONENTS

14.1

AES3 Receiver External

Components

The CS8415A AES3 receiver is designed to accept

both the professional and consumer interfaces.

The digital audio specifications for professional

use call for a balanced receiver, using XLR con-

nectors, with 110

Ω ±20% impedance. The XLR

connector on the receiver should have female pins

with a male shell. Since the receiver has a very

high input impedance, a 110

Ω resistor should be

placed across the receiver terminals to match the

line impedance, as shown in Figure 10. Although

transformers are not required by the AES, they are,

however, strongly recommended.

If some isolation is desired without the use of trans-

formers, a 0.01

µF capacitor should be placed in

series with each input pin (RXP0 and RXN0) as

shown in Figure 11. However, if a transformer is

not used, high frequency energy could be coupled

into the receiver, causing degradation in analog

performance.

Figures 10 and 11 show an optional DC blocking

capacitor (0.1

µF to 0.47 µF) in series with the ca-

ble input. This improves the robustness of the re-

ceiver,

preventing

the

saturation

the

transformer, or any DC current flow, if a DC voltage

is present on the cable.

In the configuration of systems, it is important to

avoid ground loops and DC current flowing down

the shield of the cable that could result when boxes

with different ground potentials are connected.

Generally, it is good practice to ground the shield

to the chassis of the transmitting unit, and connect

the shield through a capacitor to chassis ground at

the receiver. However, in some cases it is advan-

tageous to have the ground of two boxes held to

the same potential, and the cable shield might be

depended upon to make that electrical connection.

Generally, it may be a good idea to provide the op-

tion of grounding or capacitively coupling the shield

to the chassis.

In the case of the consumer interface, the stan-

dards call for an unbalanced circuit having a re-

ceiver impedance of 75

Ω ±5%. The connector for

the consumer interface is an RCA phono socket.

The receiver circuit for the consumer interface is

shown in Figure 12. Figure 13 shows an imple-

mentation of the Input S/PDIF Multiplexer using the

consumer interface.

The circuit shown in Figure 14 may be used when

external RS422 receivers, optical receivers or oth-

er TTL/CMOS logic outputs drive the CS8415A re-

ceiver section.

14.2

Isolating Transformer Requirements

Please refer to the application note AN134: AES

and SPDIF Recommended Transformers for re-

sources on transformer selection.

XLR

Twisted

Pair

110

Ω

110

Ω

CS8415A

RXP0

RXN0

* See Text

XLR

Twisted

Pair

110

Ω

110

Ω

CS8415A

RXP0

RXN0

0.01 F

*See Text

Figure 10. Professional Input Circuit

Figure 11. Transformerless Professional Input Circuit

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