CS4265 Datasheet, PDF (49/53 Pages) Cirrus Logic – 105 dB, 24-Bit, 192 kHz Stereo Audio CODEC

CS4265
APPENDIX C: EXTERNAL IEC60958-3 TRANSMITTER COMPONENTS
This section details the external components required to interface the IEC60958-3 transmitter to cables and fiber-
optic components.
C.1 IEC60958-3 Transmitter External Components
The IEC60958-3 specifications call for an unbalanced drive circuit with an output impedance of 75 Ω ± 20% 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 42 provides the proper output impedance and drive level using standard 1% resistors. If VD is driven
from +3.3 V, use resistor values of 243 Ω in place of the 374 Ω resistor and a 107 Ω resistor in place of the 90.9 Ω
resistor. The standard connector for a consumer application is an RCA phono socket.
The TXOUT pin may be used to drive TTL or CMOS gates as shown in Figure 43. This circuit may be used for optical
connectors for digital audio as they typically implement TTL or CMOS compatible inputs. This circuit is also useful
when driving multiple digital audio outputs as RS422 line drivers typically implement TTL compatible inputs.
TXOUT
CS4265
3 7 4 -R _TXP
90.9 Ω
RCA
Phono
Figure 42. Consumer Output Circuit (VD = 5 V)
TXOUT
CS4265
TTL or
CMOS Gate
Figure 43. TTL/CMOS Output Circuit
C.2 Isolating Transformer Requirements
Please refer to the application note AN134: AES and SPDIF Recommended Transformers for resources on trans-
former selection.
DS657A2
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