[Altera Corporation]

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.

TerminatorTM technology in StratixTM and Stratix GX devices helps prevent reflections, improving signal integrity. To address these issues, Stratix and Stratix GX devices have driver impedance matching and onchip 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.