AMD-762 Datasheet, PDF (21/122 Pages) Advanced Micro Devices – System Controller

24416C—December 2001
Preliminary Information
AMD-762™ System Controller Data Sheet
Many Segments
VTT
Part of Output Transistors
INP
Transmission Line
+
OUT
INN
V_TT/2
-
Driver
Receiver
Figure 3. Push-Pull Transmission Line Example
The dynamic compensation scheme implements a dummy
driver with characteristics exactly matching the normal driver.
An external precision resistor is attached, and the voltage of
the resulting voltage divider is compared to V_TT/2. The drive
strength is then adjusted until a voltage near V_TT/2 is achieved.
The output impedance then roughly matches the resistor value.
Separate compensation is performed for the N and P
transistors. The drive strength is changed in small steps when
no data is being driven. Refer to Figure 4.
VTT
50 Ohms + 1%
INP
+
-
V_TT/2
INN
Dummy Driver
Figure 4. Dummy Load with External Compensation Resistors
50 Ohms + 1%
Chapter 2
Functional Operation
9