STA120D STMicroelectronics, STA120D Datasheet - Page 12

• Manufacturer Part Number: STA120D
• Description: IC RECEIVER AUDIO DIGITAL 28SOIC
• Manufacturer: STMicroelectronics
• Type: Digital Audio Interface Receiverr

Specifications of STA120D

• Mounting Type: Surface Mount
• Package / Case: 28-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Applications: -
• Other names: 497-3942-5; 497-3942-5; 497-3943-5

STA120
APPENDIX A: RS422 RECEIVER INFORMATION
The RS422 receivers on the STA120 is designed to receive both the professional and consumer interfac-
es, and meet all specifications listed in the digital audio standards. Figure 6 illustrates the internal sche-
matic of the receiver portion of both chips. The receiver has a differential input. A Schmitt trigger is
incorporated to add hysteresis which prevents noisy signals from corrupting the phase detector.
Figure 6. RS422 Receiver Internal Circuit
Professional Interface
The digital audio specifications for professional use call for a balanced receiver, using XLR connectors,
with 110
shell.) Since the receiver has a very high impedance, a 110
er terminals to match the line impedance, as shown in figure 7, and, since the part has internal biasing,
no external biasing network is needed. If some isolation is desired without the use of transformers, a
0.01 F capacitor should be placed on the input of esch pin (RXP and RXN) as shown in Figure 8. How-
ever, if transformers are not used, high frequency energy could be coupled between transmitter and re-
ceiver causing degradation in analog performance.
Although transformers are not required by AES they are strongly recommended. The EBU requires trans-
formers. Figure 7 and 8 show an optional DC blocking capacitor on the transmission line. A 0.1 to 0.47 F
ceramic capacitor may be used to block any DC voltage that is accidentally connected to the digital audio
receiver. The use of this capacitor is an issue of robustness s the digital audio transmission line does not
have a DC voltage component.
Figure 7. Professional Input Circuit
Figure 8. Transformerless Professional Circuit
12/15
±20% impedance. (The XLR connector on the receiver should have female pins with a male
RXP
RXN
TWISTED
TWISTED
110
110
PAIR
PAIR
XLR
XLR
1K
1K
1
1
i x
(*)See Text
(*)See Text
110
0.01 F
0.01 F
D98AU984A
D98AU985A
110
K-i x
resistor should be placed across the receiv-
RXN
RXN
RXP
RXP
D98AU983