Ferroelectric random access memory and methods of its operation
Abstract
A ferroelectric random access memory device contains columns of ferroelectric memory cells, each column of memory cells being coupled to a distinct bit line. Each memory cell is selectively coupled to a corresponding bit line by an access control transistor so that only one memory cell in the column is coupled to the bit line at a time. To read the data stored in a selected memory cell reads, the cell is strobed twice, separately sampling the output voltage generated each time. Since the first read is a destructive read, the second read operation always reads the cell in its "0" state. Then the two sampled outputs are compared, and if the first reading exceeds the second by at least a threshold amount then a "1" output value is generated. Otherwise a "0" is the output value. In a preferred embodiment, the time delay between strobing the memory cell and sampling its output is made longer the first time that the cell is read than for the second time that the cell is read. In this way, if the cell is storing a "0" bit, the first read will produce an output voltage that is smaller than it would have been had the first read not been delayed, which helps to ensure that cells storing "0" bit values are properly sensed.

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Projected expiry passed 8 November 2011, 14.9 years ago.
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1 sheet
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Every citation, both waysCites: the store holds 2 of 3
| Document | Relation | Office | Category | Cited during |
|---|---|---|---|---|
| EP0293798A2 | Cites | European Patent Office (EPO) | Y | Search report |
| EP0359404A2 | Cites | European Patent Office (EPO) | A | Search report |
7 members in 4 offices
Priority claims4
| Document | Office | Kind | Date |
|---|---|---|---|
| 616605 | United States of America | – | |
| 61660590 | United States of America | A | |
| 61660590 | United States of America | A | |
| US19900616605 | – | – | – |
Members7
| Document | Office | Kind | |
|---|---|---|---|
| US5086412A | United States of America | A | |
| EP0486901A2 | European Patent Office (EPO) | A2 | |
| KR920010639A | Republic of Korea | A | |
| JPH04283489A | Japan | A | |
| EP0486901A3This record | European Patent Office (EPO) | A3 | |
| KR100205464B1 | Republic of Korea | B1 | |
| JP3213356B2 | Japan | B2 |
8 legal events, as the office reported them to INPADOC
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|---|---|---|
| Application deemed to be withdrawnWithdrawn18D | 18D | |
| Information on the status of an ep patent application or granted ep patentGrantedSTATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWNSTAA | STAA | |
| First examination report despatched17Q | 17Q | |
| Request for examination filed17P | 17P | |
| Designated contracting statesAK | AK | |
| Search report despatchedORIGINAL CODE: 0009013PUAL | PUAL | |
| Designated contracting statesAK | AK | |
| Public reference made under article 153(3) epc to a published international application that has entered the european phaseORIGINAL CODE: 0009012PUAI | PUAI |
Numbers
- Publication
- 0486901
- Publication, DOCDB
- 0486901
- Publication, EPODOC
- EP0486901
- Application
- 119070
- Application, DOCDB
- 91119070
- Application, EPODOC
- EP19910119070
Titles3
- German
- Ferroelektrischer Speicher und sein Betriebsverfahren
- English
- Ferroelectric random access memory and methods of its operation
- French
- Mémoire ferro-électrique et méthodes de son opération
Classification
- CPC, 2
- G11C11/22
- G11C11/407
- IPC, 2
- G11C11 22
- G11C14 00
Designated states5
- Contracting states, 5
- Germany
- France
- United Kingdom
- Italy
- Netherlands (Kingdom of the)