Patent ID: 7542343

Claim:
A memory device, comprising: a memory cell, wherein a floating gate MOS transistor serves as a storage device storing low threshold data or high threshold data in a charge trap region between a body and a control gate; a memory cell array, wherein a plurality of memory cells is serially connected to configure NAND flash memory, one side of the memory cell array is connected to a segment write line through a write select transistor and the other side of the memory cell array is connected to a segment read line through a read select transistor; a segment write buffer driving the segment write line; a segment read circuit including a pre-charge transistor to set the segment read line, a read transistor to measure discharge time of the segment read line and a select transistor to activate the read transistor, where the select transistor configures a MOS output portion; a block read circuit connecting to the MOS output portion of the segment read circuit, which generates a time-dependant voltage output; a latch circuit storing the time-dependant voltage output of the block read circuit through a read path; and a main memory column, wherein a plurality of memory cell arrays having main memory cells is connected to the segment read circuit, the main memory cells store low threshold data or high threshold data, and a plurality of segment read circuits is connected to the block read circuit; a reference memory column, wherein a plurality of memory cell arrays having reference memory cells is connected to the segment read circuit, the reference memory cells store low threshold data, and a plurality of segment read circuits is connected to the block read circuit; and a latch control circuit, wherein a delay circuit receives a reference signal which is generated by the reference memory column, and the delay circuit delays the reference signal to generate a locking signal which locks the latch circuit before receiving high threshold data from the main memory column or the reference memory column.