CS8420 CIRRUS [Cirrus Logic], CS8420 Datasheet - Page 70

• Manufacturer Part Number: CS8420
• Description: DIGITAL AUDIO SAMPLE RATE CONVERTER
• Manufacturer: CIRRUS [Cirrus Logic]

15. APPENDIX A: EXTERNAL
This section details the external components re-
quired to interface the AES3 transmitter and re-
ceiver to cables and fiber-optic components.
15.1 AES3 Transmitter External
The output drivers on the CS8420 are designed to
drive both the professional and consumer interfac-
es. The AES3 specification for professional/broad-
cast use calls for a 110
balanced drive capability. Since the transmitter
output impedance is very low, a 110
should be placed in series with one of the transmit
pins. The specifications call for a balanced output
drive of 2-7 volts peak-to-peak into a 110
with no cable attached. Using the circuit in
Figure 32, the output of the transformer is short-
circuit protected, has the proper source impedance,
and provides a 5 volt peak-to-peak signal into a
110
attached to an XLR connector with male pins and a
female shell, and with pin 1 of the connector
grounded.
In the case of consumer use, the IEC60958 specifi-
cations call for an unbalanced drive circuit with an
output impedance of 75
of 0.5 V peak-to-peak ±20% when measured across
a 75
Figure 33 only uses the TXP pin and provides the
proper output impedance and drive level using
70
CS8420
AES3/SPDIF/IEC60958
TRANSMITTER AND RECEIVER
COMPONENTS
load. Lastly, the two output pins should be
Components
Figure 32. Professional Output Circuit
load using no cable. The circuit shown in
TXN
TXP
110
source impedance and a
and a output drive level
1
resistor
XLR
load
standard 1% resistors. The connector for a consum-
er application would be an RCA phono socket. This
circuit is also short circuit protected.
The TXP pin may be used to drive TTL or CMOS
gates as shown in Figure 34. This circuit may be
used for optical connectors for digital audio since
they usually have TTL or CMOS compatible in-
puts. This circuit is also useful when driving multi-
ple digital audio outputs since RS422 line drivers
have TTL compatible inputs.
15.2 AES3 Receiver External Components
The CS8420 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
on the receiver should have female pins with a male
shell. Since the receiver has a very high input im-
pedance, a 110
the receiver terminals to match the line impedance,
as shown in Figure 35. Although transformers are
not required by the AES, they are, however, strong-
ly recommended.
If some isolation is desired without the use of trans-
formers, a 0.01 F capacitor should be placed in se-
CS8420
CS8420
Figure 34. TTL/CMOS Output Circuit
Figure 33. Consumer Output Circuit
TXN
TXP
TXN
TXP
±20% impedance. The XLR connector
374
90.9
resistor should be placed across
TTL or
CMOS Gate
CS8420
DS245PP2
RCA
Phono