ICS843034 Datasheet, PDF (15/23 Pages) Integrated Circuit Systems – MULTI-RATE 3.3V, 2.5V LVPECL FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
PRELIMINARY
ICS843034
FEMTOCLOCKS™
MULTI-RATE 3.3V, 2.5V LVPECL FREQUENCY SYNTHESIZER
DIFFERENTIAL CLOCK INPUT INTERFACE
The CLK /nCLK accepts LVDS, LVPECL, LVHSTL, SSTL, HCSL
and other differential signals. Both V_SWING and V_OH must meet the
V_PP and V_CMR input requirements. Figures 4A to 4D show inter-
face examples for the HiPerClockS CLK/nCLK input driven by
the most common driver types. The input interfaces suggested
here are examples only. Please consult with the vendor of the
driver component to confirm the driver termination requirements.
For example in Figure 4A, the input termination applies for ICS
HiPerClockS LVHSTL drivers. If you are using an LVHSTL driver
from another vendor, use their termination recommendation.
1.8V
Zo = 50 Ohm
Zo = 50 Ohm
LVHSTL
ICS
HiPerClockS
LVHSTL Driver
3.3V
CLK
nCLK _HiPerClockS
Input
R1
R2
50
50
3.3V
Zo = 50 Ohm
LVPECL
Zo = 50 Ohm
3.3V
CLK
nCLK _HiPerClockS
Input
R1
R2
50
50
R3
50
FIGURE 4A. HIPERCLOCKS CLK/nCLK INPUT DRIVEN BY
ICS HIPERCLOCKS LVHSTL DRIVER
FIGURE 4B. HIPERCLOCKS CLK/nCLK INPUT DRIVEN BY
3.3V LVPECL DRIVER
3.3V
Zo = 50 Ohm
LVPECL
Zo = 50 Ohm
3.3V
R3
R4
125
125
3.3V
CLK
nCLK _HiPerClockS
Input
R1
R2
84
84
3.3V
Zo = 50 Ohm
LVDS_Driv er
R1
100
Zo = 50 Ohm
3.3V
CLK
nCLK _{Receiv er}
FIGURE 4C. HIPERCLOCKS CLK/nCLK INPUT DRIVEN BY
3.3V LVPECL DRIVER
FIGURE 4D. HIPERCLOCKS CLK/nCLK INPUT DRIVEN BY
3.3V LVDS DRIVER
RECOMMENDATIONS FOR UNUSED INPUT AND OUTPUT PINS
INPUTS:
CRYSTAL INPUT:
For applications not requiring the use of the crystal oscillator
input, both XTAL_IN and XTAL_OUT can be left floating.
Though not required, but for additional protection, a 1kΩ
resistor can be tied from XTAL_IN to ground.
TEST_CLK INPUT:
For applications not requiring the use of the test clock, it can
be left floating. Though not required, but for additional
protection, a 1kΩ resistor can be tied from the TEST_CLK to
ground.
OUTPUTS:
LVCMOS OUTPUT:
All unused LVCMOS output can be left floating. We
recommend that there is no trace attached.
LVPECL OUTPUT
All unused LVPECL outputs can be left floating. We
recommend that there is no trace attached. Both sides of the
differential output pair should either be left floating or
terminated.
SELECT PINS:
All select pins have internal pull-ups and pull-downs;
additional resistance is not required but can be added for
additional protection. A 1kΩ resistor can be used.
843034AY
www.icst.com/products/hiperclocks.html
15
REV. A JULY 25, 2005