vsc8122 Vitesse Semiconductor Corp, vsc8122 Datasheet - Page 3

• Manufacturer Part Number: vsc8122
• Description: Multi-rate Sonet/sdh Clock And Data Recovery Ic
• Manufacturer: Vitesse Semiconductor Corp

VSC8122
G52228-0, Rev 4.1
01/05/01
Data Sheet
voltage range are specified in Table 4, High-Speed Inputs and Outputs.
Clock Recovery
vided to the VSC8122.
Table 1: Input Data Rate Select
is a phase error between the incoming data and the on-chip Voltage-Controlled Oscillator (VCO), the loop filter
raises or lowers the control voltage of the VCO to null the phase difference.
caler) and the recovered clock divided by 128. In the event of the loss of an input signal, or if the input is switch-
ing randomly, the VCO will move in one direction. At the time the VCO differs by more than 1MHz from the
REFCK based 2.48832GHz rate, the lock detector will assert the LOL output. LOL is designed to be asserted
from between 2.3µs and 100µs after the interruption of data. The VCO will continue to be frequency-locked at
approximately 1MHz off of the REFCK based 2.48832GHz rate.
incoming data. Hysteresis is provided which delays the deassertion of LOL until approximately 160µs following
the restoration of valid data.
is more than approximately 25% above or below the expected value.
Outputs can also be AC terminated as shown in Figure 3. The output differential voltage and common-mode
The VSC8122 has a selectable input data rate. Two pins (FSEL0 and FSEL1) select the data rate to be pro-
The incoming data is presented both to the clock recovery circuit and the data retiming circuit. When there
The lock detector monitors the frequency difference between the REFCK (optionally divided by a pres-
When NRZ data is again presented at the data input, the phase detector will permit the VCO to lock to the
The NOREF output will go high to indicate that there is no signal on the REFCK input, or that the REFCK
155.52Mb/s or 156.25Mb/s
1.24416Gb/s or 1.25Gb/s
2.48832Gb/s or 2.5Gb/s
622.08Mb/s or 625Mb/s
Input Data Rate
CO+ / DO+
CO- / DO-
Figure 3: High-Speed Clock and Data Output AC Termination
© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012
Tel: (800) VITESSE • FAX: [phone] • Email: [e-mail]
VSC8122
VITESSE
100Ω
100Ω
SEMICONDUCTOR CORPORATION
V
V
CC
CC
Internet: www.vitesse.com
0.1µF
0.1µF
Z
Z
FSEL0
o
o
= 50Ω
= 50Ω
0
1
0
1
Clock and Data Recovery IC
V
V
TERM
Multi-Rate SONET/SDH
TERM
50Ω
50Ω
FSEL1
0
0
1
1
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