Rambus - Another toll plaza

United States Patent 6,909,387
Li June 21, 2005

Circuit, apparatus and method for improved current distribution of output drivers enabling improved calibration efficiency and accuracy

Abstract
A circuit, apparatus and method for efficiently and accurately calibrating an output driver current are provided in embodiments of the present invention. In an embodiment of the present invention, a circuit comprises a first digital-to-analog converter ("DAC") that generates a first current. A first transistor is coupled to the first DAC and generates a first biasing current responsive to the first current. A second DAC is coupled to the first transistor and generates a first control current responsive to the first biasing current. According to an embodiment of the present invention, the first and second DACs are binary weighted control DACs. According to an embodiment of the present invention, the binary weighted values of the second DAC are obtained in response to a calibration signal generated by a controller. According to an embodiment of the present invention, the first DAC is an M-bit DAC and the second DAC is an N-bit DAC, wherein M is less than N. According to an embodiment of the present invention, the circuit is in a memory device and a controller generates calibration signals.

Inventors: Li; Yingxuan (Cupertino, CA)
Assignee: Rambus Inc. (Los Altos, CA)
Appl. No.: 695569
Filed: October 28, 2003

Hat tip to FinzToRite of the Pinehurst Thread for the link.