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RECEIVER INPUT INTERFACING
(1)Inserta0.1 Fcap common-modeDCvoltage.m acitorwhenblocking
1:1
110W
0.1 Fm
0.1 Fm
ToRX+
T Ro -X
3
2
1
XLR
DigitalInput
110 BW alanced
C
(1)
(1)Inserta0.1 Fcap common-modeDCm acitorwhenblocking components.
1:1
75W
0.1 Fm
0.1 Fm
ToRX+
ToRX-
Dig tai lInput
75 UnbalanW ced
(RCAorBNCconnector)
C
(1)
(a)Transformer-CoupledUnbalancedLineInterface
75W
0.1 Fm
0.1 Fm
ToRX+
ToRX-
DigitalInput
75 UnbalanW ced
(RCAorBNCconnector)
(b)UnbalancedLineInterfaceWithoutTransformer
SRC4382
SBFS030C – JANUARY 2006 – REVISED SEPTEMBER 2007
This section details the recommended interfaces for the SRC4382 line receiver inputs. Balanced and unbalanced
line interfaces, in addition to optical receiver and external logic interfacing, will be discussed.
For professional digital audio interfaces, 110 Ω balanced line interfaces are either required or preferred.
Transformer coupling is commonly employed to provide isolation and to improve common-mode noise rejection.
Figure 83 shows the recommended transformer-coupled balanced line receiver interface for the SRC4382. The
transformer is specified for a 1:1 turn ratio, and should exhibit low inter-winding capacitance for best
performance. Due to the DC bias on the line receiver inputs, 0.1 μ F capacitors are utilized for AC-coupling the
transformer to the line receiver inputs. On the line side of the transformer, an optional 0.1 μ F capacitor is shown
for cases where a DC bias may be applied at the transmitter side of the connection. The coupling capacitors
should be surface-mount ceramic chip type with an X7R or C0G dielectric.
Figure 83. Transformer-Coupled Balanced Input Interface
Unbalanced 75 Ω coaxial cable interfaces are commonly employed in consumer and broadcast audio
applications. Designs with and without transformer line coupling may be utilized. Figure 84 (a) shows the
recommended 75 Ω transformer-coupled line interface, which shares many similarities to the balanced design
shown in Figure 83 . Once again, the transformer provides isolation and improved noise rejection. Figure 84 (b)
shows the transformer-free interface, which is commonly used for S/PDIF consumer connections.
Figure 84. Unbalanced Line Input Interfaces
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