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87973DYI
www.idt.com
REV. D AUGUST 11, 2010
12
ICS87973I
LOW SKEW, 1-TO-12
LVCMOS / LVTTL CLOCK MULTIPLIER/ZERO DELAY BUFFER
FIGURE 5C. CLK/NCLK INPUT DRIVEN BY
3.3V LVPECL DRIVER
FIGURE 5B. CLK/NCLK INPUT DRIVEN BY
3.3V LVPECL DRIVER
FIGURE 5D. CLK/NCLK INPUT DRIVEN BY
3.3V LVDS DRIVER
3.3V
R1
50
R3
50
Zo = 50 Ohm
LVPECL
Zo = 50 Ohm
HiPerClockS
CLK
nCLK
3.3V
Input
R2
50
Zo = 50 Ohm
Input
HiPerClockS
CLK
nCLK
3.3V
R3
125
R2
84
Zo = 50 Ohm
3.3V
R4
125
LVPECL
R1
84
3.3V
DIFFERENTIAL CLOCK INPUT INTERFACE
The CLK /nCLK accepts LVDS, LVPECL, LVHSTL, SSTL, HCSL
and other differential signals. Both V
SWING and VOH must meet
the V
PP and VCMR input requirements. Figures 5A to 5D show
interface examples for the CLK/nCLK input driven by the most
common driver types. The input interfaces suggested here are
FIGURE 5A. CLK/NCLK INPUT DRIVEN BY
LVHSTL DRIVER
examples only. Please consult with the vendor of the driver
component to confirm the driver termination requirements. For
example in Figure 5A, the input termination applies for LVHSTL
drivers. If you are using an LVHSTL driver from another
vendor, use their termination recommendation.
1.8V
R2
50
Input
LVHSTL Driver
ICS
HiPerClockS
R1
50
LVHSTL
3.3V
Zo = 50 Ohm
HiPerClockS
CLK
nCLK
Zo = 50 Ohm
R1
100
3.3V
LVDS_Driv er
Zo = 50 Ohm
Receiv er
CLK
nCLK
3.3V
INPUTS:
CLK INPUT:
For applications not requiring the use of a clock input, it can
be left floating. Though not required, but for additional
protection, a 1k
Ω resistor can be tied from the CLK input to
ground.
CLK/nCLK INPUT:
For applications not requiring the use of the differential input,
both CLK and nCLK can be left floating. Though not required,
but for additional protection, a 1k
Ω resistor can be tied from
CLK to ground.
LVCMOS CONTROL PINS:
All control pins have internal pull-ups or pull-downs; additional
resistance is not required but can be added for additional
protection. A 1k
Ω resistor can be used.
RECOMMENDATIONS FOR UNUSED INPUT AND OUTPUT PINS
OUTPUTS:
LVCMOS OUTPUT:
All unused LVCMOS output can be left floating. There should
be no trace attached.