
87949AYI
www.idt.com
REV. C AUGUST 5, 2010
8
ICS87949I
LOW SKEW,
÷1, ÷2
CLOCK GENERATOR
LVPECL CLOCK INPUT INTERFACE
The PCLK /nPCLK accepts LVPECL, CML, SSTL and other
differential signals. Both V
SWING and VOH must meet the
V
PP and VCMR input requirements. Figures 1A to 1F show
interface examples for the PCLK/nPCLK input driven by the
most common driver types. The input interfaces suggested
here are examples only. If the driver is from another
vendor, use their termination recommendation. Please
consult with the vendor of the driver component to confirm
the driver termination requirements.
FIGURE 1A.
PCLK/nPCLK INPUT DRIVEN
BY AN
OPEN COLLECTOR CML DRIVER
FIGURE 1B. PCLK/nPCLK INPUT DRIVEN
BY A
BUILT-IN PULLUP CML DRIVER
FIGURE 1C.
PCLK/nPCLK INPUT DRIVEN
BY A
3.3V LVPECL DRIVER
FIGURE 1F.
PCLK/nPCLK INPUT DRIVEN
BY A
3.3V LVDS DRIVER
PCLK/nPCLK
2.5V
Zo = 60 Ohm
SSTL
HiPerClockS
PCLK
nPCLK
R2
120
3.3V
R3
120
Zo = 60 Ohm
R1
120
R4
120
2.5V
FIGURE 1E.
PCLK/nPCLK INPUT DRIVEN
BY AN
SSTL DRIVER
HiPerClockS
PCLK
nPCLK
PCLK/nPCLK
3.3V
R2
50
R1
50
3.3V
Zo = 50 Ohm
CML
3.3V
Zo = 50 Ohm
3.3V
HiPerClockS
PCLK
nPCLK
R2
84
R3
125
Input
Zo = 50 Ohm
R4
125
R1
84
LVPECL
3.3V
Zo = 50 Ohm
C2
R2
1K
R5
100
Zo = 50 Ohm
3.3V
C1
R3
1K
LVDS
R4
1K
HiPerClockS
PCLK
nPCLK
R1
1K
Zo = 50 Ohm
3.3V
PC L K /n PC LK
3.3V
R5
100 - 200
3.3V
HiPerClockS
PCLK
nPCLK
R1
125
PCLK/nPCLK
R2
125
R3
84
C1
C2
Zo = 50 Ohm
R4
84
Zo = 50 Ohm
R6
100 - 200
3.3V LVPECL
FIGURE 1D. PCLK/nPCLK INPUT DRIVEN
BY A
3.3V LVPECL DRIVER WITH AC COUPLE
3.3V
CML Built-In Pullup
R1
100
PCLK
nPCLK
HiPerClockS
PCLK/nPCLK
Zo = 50 Ohm