Electrically programmable memory with several information bits per cell
US4964079A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 24, 1989 |
| Grant date | Oct 16, 1990 |
| Priority date | — |
| Expiry date | Apr 24, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C11/5642
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
The disclosure concerns electrically programmable memories and, notably, the memories known as EPROMs, EEPROMs, FLASH-EEPROMs. To increase the information storage capacity of a memory, it is proposed to define at least three (instead of two) sections of current coming from a cell to which reading voltages are applied. These sections correspond to n possible programmed states of the cell. Comparators define a piece of information stored, for example, in two-bit form on the outputs S1, S2. However, to ensure safety during the reading despite programming uncertainties, the cell is tested by means of additional comparators and, if the cell current measured for a programming level defined among n levels is too close to the current threshold that defines the programming threshold at this level, an operation for complementary programming of the cell is triggered.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.