CS8406-IS Cirrus Logic, CS8406-IS Datasheet - Page 39

• Manufacturer Part Number: CS8406-IS
• Description: 192 KHZ DIGITAL AUDIO INTERFACE TRANSMITTER
• Manufacturer: Cirrus Logic

14.APPENDIX A: EXTERNAL AES3/SPDIF/IEC60958 TRANSMITTER
This section details the external components required to interface the AES3 transmitter to cables
and fiber-optic components.
14.1 AES3 Transmitter External Components
The output drivers on the CS8406 are designed to drive both the professional and consumer in-
terfaces. The AES3 and IEC60958-4 specifications call for a balanced output drive of 2-7 V peak-
to-peak into a 110 Ω ± 20% load with no cable attached. Using the circuit in Figure 13, the output
of the transformer is short-circuit protected, has the proper source impedance, 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 connector grounded.
In the case of consumer use, the IEC60958-3 specification calls for an unbalanced drive circuit
with an output impedance of 75 Ω ± 20% 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 14 only uses the
TXP pin and provides the proper output impedance and drive level using standard 1% resistors.
If VL is set to +3.3 V, change 374 Ω to 243 Ω and change 90.9 Ω to 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 15. 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 digital audio outputs since RS422 line driv-
ers have TTL compatible inputs.
14.2 Isolating Transformer Requirements
Please refer to the application note AN134: AES and SPDIF Recommended Transformers for re-
sources on transformer selection.
DS580F1
COMPONENTS
Figure 13. Professional Output Circuit
CS8406
TXN
TXP
110-(R
TXP
+R
TXN
)
Figure 15. TTL/CMOS Output Circuit
CS8406
TXN
TXP
1
XLR
Figure 14. Consumer Output Circuit (VL = 5.0 V)
CS8406
TTL or
CMOS Gate
TXN
TXP
90.9 Ω
374-R
TXP
CS8406
RCA
Phono
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