Non-volatile electrically alterable semiconductor memory for analog and digital storage
US5969987A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 3, 1999 |
| Grant date | Oct 19, 1999 |
| Priority date | — |
| Expiry date | Feb 3, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C7/16
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Methods and apparatus for achieving analog storage in a non-volatile memory array. The array consists of memory cells that utilize Fowler-Nordheim tunneling for erasure and hot electron injection for programming. Writing into a cell is performed by an initial erasure followed by a controlled sequence of program operations during which the cell is programmed in small increments. The stored voltage is read after each program step and when the voltage read back from the cell is equal or just beyond the desired analog level, the sequence of program steps is terminated. The read condition for the cell applies a positive voltage to the drain or common line and a positive voltage to the control gate. The source is connected through a load device to a negative (ground) supply. The output from the cell is the actual voltage that exists at the source node. There is no current sensing or comparison with a reference voltage to determine the output state. A digital number can be represented by assigning a specific analog level to a digital number. The range of digital numbers that can be represented is determined by the analog voltage range divided by the accuracy to which the voltage may be st…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.