USPTO approves another Rambus toll plaza

United States Patent 6,980,020

Best, et al. December 27, 2005

Calibration methods and circuits for optimized on-die termination

Abstract
Described are on-die termination (ODT) systems and methods that facilitate high-speed communication between a transmitter die and a receiver die interconnected via one or more signal transmission lines. An ODT control system in accordance with one embodiment calibrates and maintains the termination resistances for the signal transmission lines. The ODT control system derives a number of calibration currents from precision voltage and resistance references and distributes the reference currents to a number of transmitters. Each transmitter then derives an ODT calibration signal using the respective reference current and another precision resistor, and then employs the calibration signal to calibrate local termination elements. Distributing calibrated currents provides excellent noise immunity, while limiting the requisite number of external voltage references reduces cost.

Inventors: Best; Scott C. (Palo Alto, CA); Wong; Anthony Koon (Daly City, CA); Leung; David (Cupertino, CA)

Assignee: Rambus Inc. (Los Altos, CA)

Appl. No.: 741172

Filed: December 19, 2003

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