VSC8122-FEC 查看數據表（PDF） - Vitesse Semiconductor
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VSC8122-FEC Datasheet PDF : 14 Pages
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Data Sheet
VSC8122-FEC
VITESSE
SEMICONDUCTOR CORPORATION
Multi-Rate SONET/SDH FEC
Clock and Data Recovery IC
Outputs can also be AC terminated as shown in Figure 3. The output differential voltage and common-
mode voltage range are specified in Table 4, High-Speed Inputs and Outputs.
Figure 3: High-Speed Clock and Data Output AC Termination.
VSC8122-FEC
VCC
100Ω
CO+ / DO+
0.1 µF
0.1 µF
CO- / DO- 100Ω
Zo = 50Ω
Zo = 50Ω
VTERM
50Ω
50Ω
VCC
VTERM
Clock Recovery
The VSC8122-FEC has a selectable input data rate. Two pins (FSEL0 and FSEL1) select the data rate to be
provided to the VSC8122-FEC.
Table 1: Input Data Rate Select
Input Data Rate
2.488Gb/s - 2.66606Gb/s
1.244Gb/s or 1.25Gb/s
622Mb/s or 625Mb/s
155.52Mb/s or 156.25Mb/s
FSEL0
0
1
0
1
FSEL1
0
0
1
1
The incoming data is presented both to the clock recovery circuit and the data retiming circuit. When there
is a phase error between the incoming data and the on-chip VCO, the loop filter raises or lowers the control volt-
age of the VCO to null the phase difference.
The lock detector monitors the frequency difference between the REFCK (optionally divided by a pres-
caler), and the recovered clock divided by 128. In the event of the loss of an input signal, or if the input is
switching randomly, the VCO will move in one direction. At the time the VCO differs by more than 1MHz from
the REFCK based 2.488GHz rate (up to 2.66606Gb/s FEC), 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 (up to 2.66606Gb/s
FEC).
When NRZ data is again presented at the data input, the phase detector will permit the VCO to lock to the
incoming data. Hysteresis is provided which delays the deassertion of LOL until approximately 160us follow-
ing the restoration of valid data.
G52300-0, Rev 4.1
03/01/01
© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012
Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com
Internet: www.vitesse.com
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