Nonvolatile semiconductor memory device having suitable writing efficiency
US5682346A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 29, 1996 |
| Grant date | Oct 28, 1997 |
| Priority date | — |
| Expiry date | Mar 29, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C16/10
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
According to the present invention, a voltage level for boosting a writing voltage to be supplied to memory cells of a memory cell array, and writing time are optimized in consideration of writing efficiency and a distribution of threshold voltage. A boosting circuit boosts the writing voltage to be supplied to memory cells. A counter counts the number of writing times in accordance with a signal of a timer. The timer outputs the signal used to count the number of writing times at a fixed interval from a first writing time until an arbitrary writing time in counting a predetermined number of writing times by the counter and to count the number of writing times at an interval when the number of writing times is gradually increased after the arbitrary writing time in order to control supplying time of the writing voltage to the memory cells. Additionally, a voltage control circuit gradually divides a boost level due to the boosting circuit in accordance with the arbitrary number of writing times until the writing voltage reaches a predetermined upper limit, and maintains the writing voltage when the writing voltage reaches the predetermined upper limit.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.