Cirrus-logic CS8406 User Manual download pdf (Page 35)

DS580F6 35

CS8406

15.APPENDIX A: EXTERNAL AES3/SPDIF/IEC60958 TRANSMITTER

COMPONENTS

This section details the external components required to interface the AES3 transmitter to cables and fiber-optic

components.

15.1 AES3 Transmitter External Components

The output drivers on the CS8406 are designed to drive both the professional and consumer interfaces. The

AES3 and IEC60958-4 specifications call for a balanced output drive of 2-7 V peak-to-peak into a 110

 ±

20% load with no cable attached. Using the circuit in Figure 14, the output of the transformer is short-circuit

protected, has the p roper source impedance, and provides a 5 V peak-to-peak signal into a 110

 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 out-

put impedance of 75

 ± 20% and a output drive level of 0.5 V peak-to-peak ± 20% when measured across

a 75

 load using no cable. The circuit shown in Figure 15 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

to 243 

and change 90.9  to 107 . 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 16. 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 drivers have TTL compatible inputs.

15.2 Isolating Transformer Requirements

Please refer to the application note AN134: AES and SPDIF Recommended Transformers for resources on

transformer selection.

374-R

TXP

90.9



TXP

TXN

RCA

Phono

CS8406

110-(R

TXP

TXN

)

TXP

TXN

XLR

Pin 1

CS8406

Figure 14. Professional Output Circuit Figure 15. Consumer Output Circuit (VL = 5.0 V)

TXP

TXN

TTL or

CMOS Gate

CS8406

Figure 16. TTL/CMOS Output Circuit

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Cirrus-logic CS8406 User Manual Page 35

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