Drain side sensing scheme for virtual ground flash eprom array with adjacent bit charge and hold

Abstract

A system is disclosed for producing an indication of the logical state of a flash memory cell for virtual ground flash memory operations. The system comprises a bit line charge and hold circuit which is operable to apply a read sense voltage (e.g., about 1.2 volts) to a bit line associated with the drain terminal of a cell of the flash array adjacent to the cell which is sensed, wherein the applied drain terminal voltage is substantially the same as the cell sense voltage (e.g., about 1.2 volts) applied to the drain terminal bit line of the selected memory cell to be sensed. The system further includes a selective bit line decode circuit which is operable to select the bit lines of a memory cell to be sensed and the bit line of an adjacent cell, and a core cell sensing circuit which is operable to sense a core cell sense current at a bit line associated with a drain terminal of the selected memory cell to be sensed during memory read operations, and produce an indication of the flash memory cell logical state, which is substantially independent of charge sharing leakage current to an adjacent cell.