CS8427-CSZ datasheet(50/59 Pages) CIRRUS

50 / 59 page

CS8427

DS477F3

17.3

AES3 Receiver External

Components

The CS8427 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 23. 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 (RXP and RXN) as

shown in Figure 24. However, if a transformer is

not used, high frequency energy could be coupled

into the receiver, causing degradation in analog

performance.

Figure 23 and Figure 24 show an optional DC

blocking capacitor (0.1

µF to 0.47 µF) in series

with the cable input. This improves the robustness

of the receiver, preventing the saturation of 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 25.

The circuit shown in Figure 26 may be used when

external RS422 receivers, optical receivers or oth-

er TTL/CMOS logic outputs drive the CS8427 re-

ceiver section.

17.4

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

CS8427

RXP

RXN

0.01 F

* See Text

Figure 23. Professional Input Circuit

Figure 24. Transformerless Professional Input Circuit

XLR

Twisted

Pair

110

Ω

110

Ω

CS8427

RXP

RXN

0.01 F

*See Text

RCA Phono

RXP

RXN

CS8427

Coax

Ω

0.01 F

Figure 25. Consumer Input Circuit

Figure 26. TTL/CMOS Input Circuit

RXP

RXN

CS8427

0.01 F

TTL/CMOS

Gate

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