Method for maintaining the memory content of non-volatile memory cells
US6169691A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 15, 1999 |
| Grant date | Jan 2, 2001 |
| Priority date | — |
| Expiry date | Sep 15, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C16/3418
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A method for restoring the charge lost from memory cells, such as to restore the original voltage levels, within a time equivalent to the retention time. The condition of the memory cell is determined, for example, when the memory is switched on, or based on the time elapsed since the previous programming/restoration, or based on the difference between the present threshold voltage of the reference cells and the original threshold voltage of the (suitably stored) reference cells, or when predetermined operating conditions occur. This makes it possible to prolong the life of nonvolatile memories, in particular of multilevel type, wherein the retention time decreases as the number of levels (bits/cell) is increased.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.