A microcontroller with 100 K bytes embedded flash EEPROM

Abstract

As application of microcontrollers to achieve a cost effective system solution becomes more pervasive, demands for higher performance and higher functional integration continue to increase for microcontrollers. Flash EEPROM with its electrical reprogrammability and high density, when integrated on chip, can provide a microcontroller with enhanced performance and versatility, and offer a more cost effective system solution. This paper presents the development of a 16 bit microcontroller with 100 Kbytes of embedded flash EEPROM, that includes a block erasable flash EEPROM module. Using the SCSG (Source-Coupled Split-Gate) flash EEPROM cell, the embedded flash memory has achieved a typical program time of 20 /spl mu/s and erase time of 20 ms. The device operates at frequency of over 25 MHz. For embedded applications, the criteria for selecting a flash EEPROM cell are different from those for a stand alone flash memory. For stand alone memory, small cell area is often the most critical factor to be considered. For embedded applications, low overall production cost of the microcontrollers with integrated flash EEPROM is often the primary concern. For this reason, a robust flash EEPROM cell that is compatible with the existing host logic process without added tight process controls is a key criterion for use in embedded applications.