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ICS843002BKI-72 REV. A NOVEMBER 21, 2007

ICS843002I-72

FEMTOCLOCKS™ VCXO BASED WCDMA CLOCK GENERATOR/JITTER ATTENUATOR

Figure 3A and Figure 5B show examples of termination for 2.5V

LVPECL driver. These terminations are equivalent to terminating

50

Ω to V

CC

- 2V. For V

CC

= 2.5V, the V

CC

- 2V is very close to ground

level. The R3 in Figure 5B can be eliminated and the termination

is shown in Figure 5C.

R2

62.5

Zo = 50 Ohm

R1

250

+

-

2.5V

2,5V LVPECL

Driv er

R4

62.5

R3

250

Zo = 50 Ohm

2.5V

VCC=2.5V

R1

50

R3

18

Zo = 50 Ohm

Zo = 50 Ohm

+

-

2,5V LVPECL

Driv er

VCC=2.5V

2.5V

R2

50

2,5V LVPECL

Driv er

VCC=2.5V

R1

50

R2

50

2.5V

Zo = 50 Ohm

Zo = 50 Ohm

+

-

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.

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.