VSC8116QP VITESSE [Vitesse Semiconductor Corporation], VSC8116QP Datasheet - Page 6

• Manufacturer Part Number: VSC8116QP
• Description: ATM/SONET/SDH 622/155Mb/s Transceiver Mux/Demux with Integrated Clock Generation
• Manufacturer: VITESSE [Vitesse Semiconductor Corporation]

ATM/SONET/SDH 622/155Mb/s Transceiver
Mux/Demux with Integrated Clock Generation
Page 6
Clock Multiplier Unit
clock used for serialization in the transmitter section. The PLL is comprised of a phase-frequency detector
(PFD), an integrating operation amplifier and a voltage controlled oscillator (VCO) configured in classic feed-
back system. The PFD compares the selected divided down version of the 622MHz VCO (CMUFREQSEL
selects divide-by ratios of 8 or 32, see Table 2) and the reference clock. The integrator provides a transfer func-
tion between input phase error and output voltage control. The VCO portion of the PLL is a voltage controlled
ring-oscillator with a center frequency of 622MHz.
amplifier through the CP1, CP2, CN1 and CN2 pins. The configuration of these external surface mounted
capacitors is shown in Figure 6. Table 1 shows the recommended external capacitor values for the configurable
reference frequencies.
controlled analog ground and power planes should be provided for the PLL portion of the circuitry. The dedi-
cated PLL power (VDDA) and ground (VSSA) pins should have quiet supply planes to minimize jitter genera-
tion within the clock synthesis unit. This is accomplished by either using a ferrite bead or a C-L-C choke (
filter) on the (VDDA) power pins. Note: Vitesse recommends a ( filter) C-L-C choke over using a ferrite bead.
All ground planes should be tied together using multiple vias.
Table 1: Recommended External Capacitor Values
Frequency
Reference
The VSC8116 uses an integrated phase-locked loop (PLL) for clock synthesis of the 622MHz high speed
The reactive elements of the integrator are located off-chip and are connected to the feedback loop of the
Good analog design practices should be applied to the board design for these external components. Tightly
[MHz]
19.44
77.76
Divide Ratio
32
8
741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: [phone]
VITESSE
VITESSE SEMICONDUCTOR CORPORATION
SEMICONDUCTOR CORPORATION
CP
0.1
0.1
CN
0.1
0.1
Type
X7R
X7R
0603/0805
0603/0805
Size
VSC8116
Data Sheet
G52220-0, Rev 4.1
+/-10%
+/-10%
Tol.
1/8/00