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Details, datasheet, quote on part number:ICS8431-21
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Datasheet text preview:
Integrated Circuit Systems, Inc.
HiPerClockSTM Application Note
3.3V LVPECL DRIVER TERMINATION
This application note provides termination examples for HiPerClockS 3.3V LVPECL drivers. The HiPerClockS 3.3V LVPECL driver is an open source/emitter driver as shown in Figure 1. Proper termination is required to ensure proper function of the device and signal integrity. There are many different termination schemes for the LVPECL drivers. This application note includes standard direct termination and AC coupled termination. The following termination approaches are only general recommendations under ideal conditions. Board designers should consult with their signal integrity engineers or verify through simulations in their system environment. The trace length and physical location of the components can affect signal integrity. The 50-Ohm transmission lines in the following diagrams indicate whether the components should be located near the driver or near the receiver.
TM
TM
VCCO
VCCO
R1
R2
P.C. Board
Q
Zo = 50
nQ
Zo = 50 R4 50 R3 50
LVPECL Driver
VEE
VCCO-2V
Figure 1 HiPerClockS
TM
LVPECL driver
Direct LVPECL Termination
The standard 3.3V LVPECL termination is shown in Figure 2. This termination scheme is used in characterization. The draw back of using this termination scheme in real applications is that it requires an additional power supply VCCO-2V = 1.3V. In actual applications, the terminations shown in Figure 3 and Figure 4 are commonly used. These termination approaches eliminate the need of 1.3V power supply. In Figure 5, R1 and R2 located near the driver serve as current paths for the LVPECL outputs. The R3=100 Ohm located near the receiving serves as matched load termination for the transmission lines.
www.icst.com/products/hiperclocks.html 1
Aug 02, 2002
Integrated Circuit Systems, Inc.
HiPerClockSTM Application Note
3.3V LVPECL DRIVER TERMINATION
VCCO=VEE+3.3V
Zo = 50
Td +
Zo = 50 VEE R2 50 VCCO-2V R1 50 Td
Figure 2 Standard 3.3V LVPECL Termination
3.3V VCCO =3.3V R1 125 Zo = 50 Td + R3 125
Zo = 50
Td
-
R2 84
R4 84
Figure 3 Equivalent 3.3V LVPECL Termination
www.icst.com/products/hiperclocks.html 2
Aug 02, 2002
Integrated Circuit Systems, Inc.
HiPerClockSTM Application Note
3.3V LVPECL DRIVER TERMINATION
VCCO=3.3V Zo = 50 Td +
Zo = 50 Td
R2 50
R1 50
R3 50
Figure 4 Equivalent 3.3V LVPECL Termination
VCCO=3.3V U1 Zo = 50 TL1 3v3 PECL Driver R3 100 Zo = 50 nTL1 R2 100-180 R1 100-180 Td Td
+
Figure 5 Termination with 100-Ohm resistor across the differential input
www.icst.com/products/hiperclocks.html 3
Aug 02, 2002
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