VSC8115
Data Sheet
AC CHARACTERISTICS
Over Recommended Operating Conditions.
Table 10. Performance Specifications
Symbol
Parameter
Min
Typ
Max
Units Condition
f
VCO Center Frequency
622.08
MHz
ppm
f
CRU’s Reference Clock Frequency
–250
+250
TOL
Tolerance
fT
OC-12/STS-12 Capture Range
500
ppm
With respect to the fixed
reference frequency.
% of UI 20% minimum transition density.
REF_CLK
CLKOUT
Clock Output Duty Cycle
45
55
16
DC
t
OC-12/STS-12 Acquistion Lock Time
µs
Valid REFCLK and device
already powered up.
LOCK
t
t
,
LVDS and LVPECL Output Rise and
Fall Times
500
ps
10% to 90%, with 100 and 5pF
capacitive equivalent load.
LOCKDET_R
LOCKDET_F
J
J
CLKOUT Jitter Generation
0.005
0.01
UI
UI
GEN_CLK
OC-12/STS-12 Jitter Tolerance
0.45
Sinusoidal input jitter of
TOL
DATAIN from 250kHz to 5MHz.
Jitter Tolerance
Jitter tolerance is the ability of the CDR to track timing variations in the received data stream. The Bellcore and ITU
specifications allow the received optical data to contain jitter, however, the amount that must be tolerated is a function
of the frequency of the jitter. At high frequencies the specifications do not require the VSC8115 to tolerate large
amounts of jitter, whereas, at low frequencies, many unit intervals (bit times) of jitter have to be tolerated. Jitter
tolerance is defined as the ratio of jitter on the output OC-N/STS-N signal to the jitter applied on the input OC-N/
STS-N signal versus frequency. The VSC8115 is designed to tolerate this jitter with margin over the specification
limits. See Figure 2. The VSC8115 obtains and maintains lock based on the data transition information. When there is
no transition on the data stream, the recovered clock frequency will be held to within 500ppm of the reference clock.
The VSC8115 can maintain lock status with a data stream carrying over 1,000 consecutive identical digits (CID).
150
Bellcore Requirement
15
1.5
0.15
0
0
10
30
300
25k
250k
2.5M
Jitter Frequency (Hz)
Figure 2. Input Jitter Tolerance Specification
6 of 12
G52272, Rev 4.2
5/14/03
VITESSE [ VITESSE SEMICONDUCTOR CORPORATION ]
