PRELIMINARY
ICS843251I-12
Integrated
Circuit
Systems, Inc.
FEMTOCLOCKS™ CRYSTAL-TO-3.3V, 2.5V
LVPECL CLOCK GENERATOR
TERMINATION FOR 2.5V LVPECL OUTPUT
Figure 4A and Figure 4B show examples of termination for 2.5V ground level. The R3 in Figure 4B can be eliminated and the
LVPECL driver.These terminations are equivalent to terminat- termination is shown in Figure 4C.
ing 50Ω to VCC - 2V. For VCC = 2.5V, the VCC - 2V is very close to
2.5V
VCC=2.5V
2.5V
2.5V
VCC=2.5V
Zo = 50 Ohm
Zo = 50 Ohm
R1
250
R3
250
+
-
Zo = 50 Ohm
Zo = 50 Ohm
+
-
2,5V LVPECL
Driv er
R1
50
R2
50
2,5V LVPECL
Driv er
R2
62.5
R4
62.5
R3
18
FIGURE 4A. 2.5V LVPECL DRIVER TERMINATION EXAMPLE
FIGURE 4B. 2.5V LVPECL DRIVER TERMINATION EXAMPLE
2.5V
VCC=2.5V
Zo = 50 Ohm
+
Zo = 50 Ohm
-
2,5V LVPECL
Driv er
R1
50
R2
50
FIGURE 4C. 2.5V LVPECL TERMINATION EXAMPLE
843251BGI-12
www.icst.com/products/hiperclocks.html
REV.A JANUARY 10, 2006
9
ICSI [ INTEGRATED CIRCUIT SOLUTION INC ]
