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:
Jul. 08, 2008
Filed:
Jan. 05, 2007
Hock C. SO, Redwood City, CA (US);
Sau C. Wong, Hillsborough, CA (US);
Hock C. So, Redwood City, CA (US);
Sau C. Wong, Hillsborough, CA (US);
SanDisk Corporation, Milpitas, CA (US);
Abstract
A multibit-per-cell non-volatile memory divides the suitable threshold voltages of memory cells into ranges corresponding to allowed states for storage of data and ranges corresponding to forbidden zones indicating a data error. A read process checks whether a threshold voltage is in a forbidden zone. Alternately, a refresh process includes reprogramming the threshold voltage into an allowed state. In the case of a flash memory, a refresh reads a sector of the memory and saves corrected data from the sector in a buffer or another sector. The corrected data from the buffer or other sector can be written back in the original sector, or the corrected data can be left in the other sector with addresses of the original sector being mapped to the other sector. Refresh process for the non-volatile memory can be performed in response to detecting a threshold voltage in a forbidden zone or periodically.