A 126.6-mm(2) and-type 512-Mb flash memory with 1.8-V power supply

A 512-Mb flash memory, which is applicable to removable flash media of port able equipment such as audio players, has been developed. The chip Is fabri cated with a 0.18-mum CMOS process on a 126.6-mm(2) die, and uses a multile vel technique (2 bit/1 cell). The memory cell is AND-type, which is suitabl e for multilevel operation. This paper reports new techniques adopted in th e 512-Mb flash memory. First, techniques for low voltage operation are desc ribed. The charge pump, control of pumps, and the reference voltage generat or are improved to generate internal voltage stably for multilevel flash me mory. Next, a method for reducing total memory cost in the removable flash media is described. A new operation mode named read-modify-write is introdu ced on the chip. This feature makes the memory system simple, because the c ontroller does not have to track sector-erase information.