Reference signal generating method and circuit for differential evaluation of the content of nonvolatile memory cells
US5541880A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 28, 1995 |
| Grant date | Jul 30, 1996 |
| Priority date | — |
| Expiry date | Mar 28, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C16/344
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
To reduce the supply voltage of a nonvolatile memory, a read reference signal is generated having a reference threshold value ranging between the maximum permissible threshold value for erased cells and the minimum permissible threshold value for written cells. To avoid reducing the maximum supply voltage, the characteristic of the read reference signal is composed of two portions: a first portion, ranging between the threshold value and a predetermined value, presents a slope lower than that of the characteristic of the memory cells and a second portion, as of the predetermined value of the supply voltage, presents the same slope as the characteristics of memory cells. The shifted-threshold, two-slope characteristic is achieved by means of virgin cells so biased as to see bias voltages lower than the supply voltage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.