Concurrent erase verify scheme for flash memory applications

摘要

A method for sensing the state of erasure of a flash (EEPROM) memory device. In one embodiment, the source voltage during erase is monitored and compared to a value determined during a characterization procedure. In a second embodiment, the rate of change of the source voltage during erase is determined and compared to a value determined during a characterization procedure. The characterization procedure correlates state of erasure with source voltages and slopes of the rate of change of source voltage versus time curve for the memory cells. The determination of the source voltage and the determination of the rate of change of the source voltage and the associated state of erasure allows modification of the erase procedure.