Using Terminator
November 2002, ver. 2.0 Application Note 209
Introduction
Signal integrity is crucial in high-speed digital designs because of
increased system speeds and clock edge rates. Designers must properly
terminate single-ended and differential signals to achieve signal integrity.
Traditionally, designers use on-board termination resistors to achieve
proper signal termination. However, these resistors take up significant
board space and can cause signal reflections (stub effects). These
reflections normally occur when a termination resistor is too far away
from the transmission line it terminates.
Terminator
TM
technology in Stratix
TM
and Stratix GX devices helps
prevent reflections, improving signal integrity. To address these issues,
Stratix and Stratix GX devices have driver impedance matching and on-
chip termination circuitry. Terminator technology includes series
termination, impedance matching, parallel termination for single-ended
I/O standards (e.g., HSTL and SSTL-2), and differential termination.
Termination resistors are adjacent to the buffers on the device, thereby
eliminating stub effects. Terminator technology minimizes the need for a
cumbersome external resistor network, thereby easing board routing and
saving board space. Figure 1 shows a footprint comparison of a device
with external termination and with Terminator technology.
This application note covers various Terminator technology types
supported by Stratix and Stratix GX devices as well as power
management.
Figure 1. Device Footprint Comparison with & without Terminator Technology
With
External
Termination
With
Terminator
Technology
Termination
Resistors
Reference
Resistors
Technology in Stratix &
Stratix GX Devices
Altera Corporation 1
AN-209-2.0