The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 04, 2009
Filed:
Feb. 08, 2008
Steven M. Clements, Raleigh, NC (US);
William P. Cornwell, Durham, NC (US);
Carrie E. Cox, Cary, NC (US);
Hayden C. Cranford, Jr., Cary, NC (US);
Vernon R. Norman, Cary, NC (US);
Steven M. Clements, Raleigh, NC (US);
William P. Cornwell, Durham, NC (US);
Carrie E. Cox, Cary, NC (US);
Hayden C. Cranford, Jr., Cary, NC (US);
Vernon R. Norman, Cary, NC (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
Substantially-accurate calibration of output impedance of a device-under-test (DUT) to within a predetermined range of allowable impedance. The DUT is part of a source series terminated (SST) serial link transmitter, in which two branches of parallel transistors each provide an impedance value when particular transistors of the parallel branch are turned on. The impedance value is added to a series-connected resistor to provide the output impedance. The DUT consists of one branch of parallel transistors in series with a resistor. Output impedance of the DUT is compared to the resistance of a reference resistor, and the comparator provides a control signal based on whether the output impedance falls within the pre-set percentage variance of the reference resistance. The control signal is processed by a FSM (finite state machine) that individually turns on or off the transistors within the parallel branch until the DUT impedance value falls within the desired range.