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. 20, 2002
Filed:
Jun. 14, 2001
Sharp Kabushiki Kaisha, Osaka, JP;
Abstract
There is provided a nonvolatile semiconductor storage device capable of securing sufficient read accuracy without providing superfluous sense time margin when there are variations in temperature and transistor characteristics. This nonvolatile semiconductor storage device includes a reference cell whose threshold value is preparatorily set to a value between a lower limit of a threshold voltage distribution in a state in which nonvolatile memory cells MC through MC have a high threshold value and an upper limit of a threshold voltage distribution in a state in which the memory cells have a low threshold value. When the characteristics of the nonvolatile memory cells MC through MC shift due to the influence of a change in temperature or the like, the characteristics of the reference cell shift so as to follow this characteristic shift. The operation timing of a sense amplifier section in read operation is generated by a control circuit, and the timing of the termination of the sense operation from among the operation timing is determined by timing control circuit (delay circuit delay and AND circuits AN and AN ) with the termination of the sense of the reference cell