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:
Jan. 28, 1992
Filed:
Dec. 22, 1989
Joseph Drori, San Jose, CA (US);
William S Jennings Check, Orangevale, CA (US);
William H Owen, III, Los Altos Hills, CA (US);
Xicor, Inc., Milpitas, CA (US);
Abstract
A variable impedance circuit for use in an external circuit is disclosed. The impedance value is selected by an external circuit. The variable impedance is generated between two terminals which are accessible for connection to external circuitry. The impedance provided between these terminals is determined by a control circuit responsive to electrical signals coupled to the control circuit. An internal register in the control circuit stores a value which specifies the impedance between the two terminals. The stored value is copied into a programmable nonvolatile read-only memory in response to a first predetermined electrical signal. Similarly, the value stored in the read-only memory is selectively copied into the internal control circuit register in response to a second predetermined electrical signal. A number of embodiments of variable impedance elements are disclosed which minimize the number of separate resistors required to achieve the equivalent resolution achievable using a series arrangement of resistors.