
IDT / ICS 3.3V LVPECL FREQUENCY SYNTHESIZER
10
ICS843256BG REV. A MAY 23, 2007
ICS843256
FEMTOCLOCKS CRYSTAL-TO-3.3V LVPECL FREQUENCY SYNTHESIZER
TERMINATION FOR 2.5V LVPECL OUTPUT
Figure 5A and Figure 5B show examples of termination for 2.5V
LVPECL driver. These terminations are equivalent to terminat-
ing 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.
FIGURE 5C. 2.5V LVPECL TERMINATION EXAMPLE
R2
50
Zo = 50 Ohm
VCCO=2.5V
R1
50
Zo = 50 Ohm
+
-
2.5V
2,5V LVPECL
Driv er
FIGURE 5B. 2.5V LVPECL DRIVER TERMINATION EXAMPLE
VCCO=2.5V
R1
50
R2
50
Zo = 50 Ohm
R3
18
2,5V LVPECL
Driv er
Zo = 50 Ohm
+
-
2.5V
FIGURE 5A. 2.5V LVPECL DRIVER TERMINATION EXAMPLE
R2
62.5
2.5V
2,5V LVPECL
Driv er
R3
250
Zo = 50 Ohm
R4
62.5
2.5V
+
-
R1
250
VCCO=2.5V