CS8405A-IS CIRRUS [Cirrus Logic], CS8405A-IS Datasheet - Page 34

• Manufacturer Part Number: CS8405A-IS
• Description: 96 kHz Digital Audio Interface Transmitter
• Manufacturer: CIRRUS [Cirrus Logic]

14. 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.
14.1
The output drivers on the CS8405A are designed
to drive both the professional and consumer inter-
faces. The AES3 specification for profession-
al/broadcast 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 V peak-to-peak into a
110 Ω load with no cable attached. Using the cir-
cuit in
short-circuit protected, has the proper source im-
pedance, and provides a 5 V 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 con-
nector grounded.
34
CS8405A
AES3/SPDIF/IEC60958 TRANSMITTER
AND RECEIVER COMPONENTS
Figure
AES3 Transmitter External
Components
Figure 11. Professional Output Circuit
TXN
TXP
11, the output of the transformer is
110-(R
TXP
+R
TXN
CS8405A
)
Figure 13. TTL/CMOS Output Circuit
TXP
TXN
1
XLR
In the case of consumer use, the IEC60958 speci-
fications call for an unbalanced drive circuit with an
output impedance of 75 Ω and a output drive level
of 0.5 V peak-to-peak ±20% when measured
across a 75 Ω load using no cable. The circuit
shown in Figure 12 only uses the TXP pin and pro-
vides the proper output impedance and drive level
using standard 1% resistors. If VL+ is driven from
+3.3 V, use resistor values of 243 Ω and 107 Ω.
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 13. This circuit may be
used for optical connectors for digital audio since
they usually have TTL or CMOS compatible inputs.
This circuit is also useful when driving multiple dig-
ital audio outputs since RS422 line drivers have
TTL compatible inputs.
14.2
Please refer to the application note AN134: AES
and SPDIF Recommended Transformers for re-
sources on transformer selection.
Isolating Transformer Requirements
TTL or
CMOS Gate
Figure 12. Consumer Output Circuit
C S 8 4 0 5 A
T X N
T X P
9 0 . 9 Ω
3 7 4 -R
CS8405A
T X P
DS469F2