Multi-bit-per-cell flash EEPROM memory with refresh
US7397697B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jan 5, 2007 |
| Grant date | Jul 8, 2008 |
| Priority date | — |
| Expiry date | Jan 5, 2027 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C2211/5634
- WIPO fieldMeasurement
- WIPO sectorInstruments
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.