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:
Apr. 17, 2001
Filed:
Oct. 13, 1999
David R. MacQuigg, Tuscon, AZ (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
An apparatus and method for performing curvature trim in a voltage reference circuit that allows a curvature error to be trimmed after the circuit has been packaged. The curvature trim may be performed by switching in segments of one or more non-linear resistors, such as n-type lightly doped drain (LDD) diffused resistors, having a curvature characteristic that is opposite to the normal band-gap curvature. Specifically, a network of non-linear resistors may be selected via selection bits stored in a non-volatile memory. Since various combinations of the resistors may be selected by programming the memory, the curvature of a band-gap reference can be adjusted after final packaging. This curvature correction method achieves a reliable and accurate correction for the curvature variations associated with various process changes.