ICS853111A Datasheet, PDF (11/19 Pages) Integrated Circuit Systems – LOW SKEW, 1-TO-10 DIFFERENTIAL-TO-2.5V/3.3V LVPECL/ECL FANOUT BUFFER

ICS853111A
LOW SKEW, 1-TO-10, DIFFERENTIAL-TO-LVPECL/ECL FANOUT BUFFER
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 terminating
50Ω to V - 2V. For V = 2.5V, the V - 2V is very close to ground
CC
CC
CC
VC C O=2. 5V
Zo = 50 Ohm
2.5V
R1
R3
250
250
2.5V
+
Zo = 50 Ohm
2,5V LVPECL
Driv er
-
R2
62.5
R4
62.5
level. The R3 in Figure 5B can be eliminated and the
termination is shown in Figure 5C.
VCCO=2.5V
Zo = 50 Ohm
Zo = 50 Ohm
2,5V LVPECL
Driv er
2.5V
+
-
R1
R2
50
50
R3
18
FIGURE 5A. 2.5V LVPECL DRIVER TERMINATION EXAMPLE
FIGURE 5B. 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 5C. 2.5V LVPECL TERMINATION EXAMPLE
TERMINATION FOR 5V LVPECL OUTPUT
This section shows examples of 5V LVPECL output termination.
Figure 6A shows standard termination for 5V LVPECL. The
termination requires matched load of 50Ω resistors pull down to
V - 2V = 3V at the receiver. Figure 6B shows Thevenin
CC
equivalence of Figure 6A. In actual application where the 3V DC
power supply is not available, this approached is normally used.
5V
PEC L
Zo = 50 Ohm
Zo = 50 Ohm
R1
R2
50
50
3V
5V
+
-
PECL
5V
PECL
Zo = 50 Ohm
Zo = 50 Ohm
5V
R3
R4
84
84
+
-
R1
R2
125
125
PECL
FIGURE 6A. STANDARD 5V LVPECL OUTPUT TERMINATION
FIGURE 6B. 5V LVPECL OUTPUT TERMINATION EXAMPLE
IDT^™ / ICS^™ 1-TO-10, LVPECL/ECL FANOUT BUFFER
11
ICS853111AY REV. C OCTOBER 25, 2007