High resolution analog storage EPROM and flash EPROM
US5638320A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 11, 1996 |
| Grant date | Jun 10, 1997 |
| Priority date | — |
| Expiry date | Jan 11, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C2211/5621
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Circuits and processes write and read analog signals in non-volatile memory cells such as EPROM and flash EPROM cells. One read process determines a memory cell's threshold voltage by slowly ramping the control gate voltage and sensing when the cell conducts. Another read process slowly ramps the source voltage of a memory cell and determines the cell's threshold voltage from the drain voltage of the memory cell. Still another read process connects a cascoding device to a memory cell and biases the memory cell in the linear region while the threshold voltage of the memory cell is determined from a voltage across a load which carries a current that mirrors the current through the memory cell. Read processes disclosed for analog memory cells also apply to binary memory cells, multilevel digital memory cells, and other applications which require precise reading of threshold voltages.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.