G52221-0, Rev. 4.1

© VITESSE SEMICONDUCTOR CORPORATION

Page 21

1/8/00

741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896

VITESSE

SEMICONDUCTOR CORPORATION

Data Sheet

VSC8117

ATM/SONET/SDH 622/155 Mb/s Transceiver Mux/Demux

with Integrated Clock Generation and Clock Recovery

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

Table 17: AC Coupling Component Values

Component

Value

Tolerance

R1

270 ohms

5%

R2

75 ohms

5%

R3

68 ohms

1%

R4

190 ohms

1%

C1, C2, C3, C4

.01uf High Frequency

PC Board Trace

PC Board Trace

DRIVER

(Optics Module)

RECEIVER

(Optics Module)

VSC8117

PECL I/O

R2

R4

C2

C1

R3

Note: Only one side of a differential signal is shown.

R1

GND

+3.3V

+5.0V

GND

GND

GND