CS8427 Cirrus Logic, CS8427 Datasheet - Page 51

• Manufacturer Part Number: CS8427
• Description: 96 kHz Digital Audio Interface Transceiver
• Manufacturer: Cirrus Logic

18.2 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 connectors,
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 im-
pedance, a 110Ω resistor should be placed across
the receiver terminals to match the line impedance,
as shown in
not required by the AES, they are, however, strong-
ly recommended.
If some isolation is desired without the use of trans-
formers, a 0.01µF capacitor should be placed in se-
ries with each input pin (RXP and RXN) as shown
in
high frequency energy could be coupled into the re-
ceiver, causing degradation in analog performance.
Figure 25
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 volt-
age is present on the cable.
In the configuration of systems, it is important to
avoid ground loops and DC current flowing down
DS477PP3
Figure
Twisted
110 Ω
Pair
Coax
75 Ω
Figure 25. Professional Input Circuit
26. However, if a transformer is not used,
Figure 27. Consumer Input Circuit
XLR
and
Figure
1
RCA Phono
Figure 26
* See Text
25. Although transformers are
75 Ω
110 Ω
show an optional DC
0.01 F
0.01 F
0.01 F
0.01 F
µ
µ
µ
µ
CS8427
RXP
RXN
CS8427
RXP
RXN
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 advanta-
geous to have the ground of two boxes held to the
same potential, and the cable shield might be de-
pended 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 standards
call for an unbalanced circuit having a receiver im-
pedance of 75 Ω ±5%. The connector for the con-
sumer interface is an RCA phono socket. The
receiver circuit for the consumer interface is shown
in
The circuit shown in
external RS422 receivers, optical receivers or other
TTL/CMOS logic outputs drive the CS8427 receiv-
er section.
18.3 Isolating Transformer Requirements
Please refer to the application note AN134: “AES
and SPDIF Recommended Transformers” for re-
sources on transformer selection.
Figure 26. Transformerless Professional Input Circuit
Figure
Twisted
110 Ω
Pair
TTL/CMOS
Figure 28. TTL/CMOS Input Circuit
27.
XLR
1
Gate
* See Text
110 Ω
Figure 28
0.01 F
0.01 F
µ
0.01 F
µ
0.01 F
may be used when
µ
µ
CS8427
RXP
RXN
CS8427
CS8427
RXP
RXN
51