Appendix A: External Aes3/Spdif/Iec60958 Transmitter And Receiver Components; Aes3 Transmitter External Components; Figure 22. Professional Output Circuit; Figure 23. Consumer Output Circuit - Cirrus Logic Crystal CS8427 Series Preliminary Product Information

13. APPENDIX A: EXTERNAL
AES3/SPDIF/IEC60958
TRANSMITTER AND RECEIVER
COMPONENTS
This section details the external components re-
quired to interface the AES3 transmitter and re-
ceiver to cables and fiber-optic components.
13.1 AES3 Transmitter External
Components
The output drivers on the CS8427 are designed to
drive both the professional and consumer interfac-
es. The AES3 specification for professional/broad-
cast use calls for a 110 Ω source impedance and a
balanced drive capability. Since the transmitter
output impedance is very low, a 110 Ω resistor
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 Ω load
with no cable attached. Using the circuit in Figure
22, the output of the transformer is short-circuit
protected, has the proper source impedance, and
CS8427
110 Ω
TXP
TXN

Figure 22. Professional Output Circuit

DS477PP1
provides a 5 volt peak-to-peak signal into a 110 Ω
load. Lastly, the two output pins should be 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 Ω and a output drive level
of 0.5 volts peak-to-peak ±20% when measured
across a 75 Ω load using no cable. The circuit
shown in Figure 23 only uses the TXP pin and pro-
vides the proper output impedance and drive level
using standard 1% resistors. The connector for a
consumer 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 24. 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.
XLR
1
CS8427
TXP
TXN

Figure 24. TTL/CMOS Output Circuit

CS8427
374 Ω
TXP
90.9 Ω
TXN

Figure 23. Consumer Output Circuit

TTL or
CMOS Gate
CS8427
RCA
Phono
49