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US 6,639,849 B2Granted
Nonvolatile semiconductor memory device programming second dynamic reference cell according to threshold value of first dynamic reference cell
AssigneeFujitsu Limited
InventorsSatoshi Takahashi, Minoru Yamashita
Life of this patent
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Abstract
In a nonvolatile semiconductor memory device, first and second dynamic reference cells are subjected to a same rewriting operation as performed to a memory cell. An average reference current is obtained from the first and second dynamic reference cells, and is compared with a current of data read from the memory cell so as to judge a level of the read data. In this configuration, the second dynamic reference cell is programmed according to a threshold value of the first dynamic reference cell.
Claims10
A nonvolatile semiconductor memory device including:
- a memory cell;
- first and second dynamic reference cells subjected to a same rewriting as performed to said memory cell;
- and
- a data judgment control circuit obtaining an average reference current from said first and second dynamic reference cells, and comparing a current of data read from said memory cell with said average reference current so as to judge said data,
- wherein said data judgment control circuit programs the second dynamic reference cell according to a threshold value of the first dynamic reference cell.
2 more elements
Dependencies are inferred from the claim text.