VITESSE
SEMICONDUCTOR CORPORATION
Data Sheet
ATM/SONET/SDH 622/155 Mb/s Transceiver Mux/Demux
with Integrated Clock Generation and Clock Recovery
VSC8117
Ground Planes
The ground plane for the components used in the High Speed interface should be continuous and not sec-
tioned in an attempt to provide isolation to various components. Sectioning of the ground planes tends to inter-
fere with the ground return currents on the signal lines. In addition, the smaller the ground planes the less
effective they are in reducing ground bounce noise and the more difficult to decouple. Sectioning of the positive
supplies can provide some isolation benefits.
Figure 12: AC Coupled High Speed I/O
VSC8117
PECL I/O
+3.3V
+5.0V
DRIVER
RECEIVER
(Optics Module)
(Optics Module)
R3
C1
C2
PC Board Trace
PC Board Trace
R2
GND
R4
GND
R1
GND
GND
Note: Only one side of a differential signal is shown.
Table 17: AC Coupling Component Values
Component
Value
Tolerance
R1
270 ohms
75 ohms
5%
5%
1%
1%
R2
R3
R4
68 ohms
190 ohms
C1, C2, C3, C4
.01uf High Frequency
G52221-0, Rev. 4.1
1/8/00
VITESSE SEMICONDUCTOR CORPORATION
741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896
Page 21
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