ICS843034 Datasheet, PDF (17/23 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
TERMINATION FOR 2.5V LVPECL OUTPUT
Figure 7A and Figure 7B show examples of termination for
2.5V LVPECL driver. These terminations are equivalent to ter-
minating
50Ω
to
V
CC
-
2V.
For
V
CC
=
2.5V,
the
V
CC
-
2V
is
very
close to ground level. The R3 in Figure 7B can be eliminated
and the termination is shown in Figure 7C.
VC CO=2. 5V
Zo = 50 Ohm
Zo = 50 Ohm
2,5V LVPECL
Driv er
2. 5V
R1
R3
250
250
2.5V
+
-
R2
62. 5
R4
62. 5
VCC O=2. 5V
Zo = 50 Ohm
Zo = 50 Ohm
2,5V LVPECL
Driv er
2.5V
+
-
R1
R2
50
50
R3
18
FIGURE 7A. 2.5V LVPECL DRIVER TERMINATION EXAMPLE
FIGURE 7B. 2.5V LVPECL DRIVER TERMINATION EXAMPLE
VCCO=2.5V
Zo = 50 Ohm
Zo = 50 Ohm
2,5V LVPECL
Driv er
2. 5V
+
-
R1
R2
50
50
FIGURE 7C. 2.5V LVPECL TERMINATION EXAMPLE
843034AY
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17
REV. A JULY 25, 2005