Rambus Inc.

Lsi Logic Corporation

David Leung

Scott C Best

Anthony Koon Wong

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.

Calibration methods and circuits for optimized on-die termination

A reference voltage generator for producing a regulated, temperature-compensated output voltage from an unregulated power supply voltage is provided herein. The reference voltage generator includes a pre-regulating circuit and a temperature-compensating circuit. The temperature compensating circuit includes a first series path comprising a first cascode current sources and a first resistor; a second series path comprising a second cascode current source, a first field effect transistor and a first diode; and a third series path comprising a third cascode current source, a second field effect transistor, a second resistor and a second diode. The first series path being connected to the second series path between the first field resistor and the first diode. The current produced by the first current source, develops a voltage across the first resistor, which varies at least as a function of the ratio of the first and second resistors, the ratio of the diode junction areas, the dimensions of the first and second field effect transistors, and the first diode thermal voltage which has a positive temperature coefficient. The voltage across the first diode has a negative temperature coefficient. The output voltage taken across both the first resistor and first diode can be made substantially temperature invariant if the resistor ratio is selected such that it amplifies the temperature coefficient of the thermal voltage so that it is substantially equal and opposite to the temperature coefficient of the first diode voltage.

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Cupertino, CA, United States of America

David Leung