Auto adjusting window placement scheme for an NROM virtual ground array
US6222768A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 26, 2000 |
| Grant date | Apr 24, 2001 |
| Priority date | — |
| Expiry date | Apr 26, 2020 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C16/349
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A virtual ground array based flash memory device includes a virtual ground array containing individual memory elements with supporting input/output circuitry. The threshold voltages of the memory elements gradually increase over operating cycles due to trapping of charge in the nitride or oxide, eventually causing errors due to the increase in threshold voltage. Internal routines are necessary to characterize the change in threshold voltages and subsequently modify the comparison circuit supplying the current used to determine whether the memory elements have attained a specific threshold. The method of automatically adjusting the window of the virtual ground array increases endurance and reliability of the virtual ground array and decreases errors caused by the increased threshold voltage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.