CS8420-CSZ datasheet(78/94 Pages) CIRRUS

78 / 94 page

DS245F4

CS8420

14. EXTERNAL AES3/SPDIF/IEC60958 TRANSMITTER AND RECEIVER

COMPONENTS

This section details the external components required to interface the AES3 transmitter and receiver to cables and

fiber-optic components.

14.1

AES3 Transmitter External Components

The output drivers on the CS8420 are designed to drive both the professional and consumer interfaces. The

AES3 specification for professional/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 volts peak-to-peak

into a 110

Ω load with no cable attached. Using the circuit in Figure 30, the output of the transformer is short-

circuit protected, has the proper source impedance, and provides a 5 volts 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 specifications 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 31 only uses the TXP pin and provides the proper output imped-

ance 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.

110-(R

TXP+RTXN)

TXP

TXN

XLR

CS8420

Figure 30. Professional Output Circuit

374-R

TXP

90.9

TXP

TXN

RCA

Phono

CS8420

Figure 31. Consumer Output Circuit

CS8420-CSZ Datasheet(PDF) 78 Page - Cirrus Logic