VITESSE

SEMICONDUCTOR CORPORATION

Data Sheet

VSC8121

2.488GHz SONET/SDH

Clock Generator

G52163-0, Rev 4.2

Page 5

04/16/01

© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012

Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com

Internet: www.vitesse.com

AC Characteristics

Table 2: AC Characteristics

NOTE: (1) ppm refers to “parts per million.” 100ppm (100/1000000) is equivalent to 0.01%. Therefore, the equivalent reference

clock frequency range in MHz for +/-100ppm tolerance is as follows:

Note that +/-100ppm tolerance for reference clock frequency more than accommodates the SONET/SDH requirement that refer-

ence clock-supplying crystals function at +/-20ppm.)

Figure 5: RMS/Peak-to-Peak Jitter (12kHz - 20MHz), REF_CLK freq = 77.76MHz

Parameter

Description

Min

Typ

Max

Units

Conditions

High-speed output clock period

—

401.9

—

ps

Reference clock duty cycle

45

—

55

%

Reference clock frequency (selectable)

—

51.84,

77.76,

or

155.52

—

MHz

∆f

RC

Reference clock frequency tolerance

-100

—

+100

ppm

(1)

Jitter generation

—

1.75

3.6

ps RMS

12kHz to 20MHz.

See Figure 5.

X 100ppm =

Acceptable Range

51.84MHz

5.184KHz

51.83MHz to 51.85MHz

77.76MHz

7.776KHz

77.75MHz to 77.78MHz

155.52MHz

15.552KHz

155.51MHz to 155.54MHz

0

20

40

60

80

100

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Case Temperature (deg C)

0

20

40

60

80

100

25

20

15

10

5

0

Case Temperature (deg C)

RMS Jitter

Pk-Pk Jitter