A comparative study of charge pumping circuits for flash memory applications

Abstract

Flash memories are now widely used in many portable electronic devices, in embedded systems and are even as replacement for computer hard disks. In flash memory systems, high-voltages (up to about 10 V) are indispensable for programming operations. In many cases, however, such programming voltages are not directly available from the supply, and are usually generated by embedded voltage converting or charge pumping circuits. These circuits produce the required programming voltage from available external supplies with voltages in the approximate range of 1-5 V. The power conversion efficiency, the chip size, the voltage regulation, as well as the loading characteristics have been the major concerns for such circuits. The present paper discusses some recently proposed charge pumping circuits for flash memory applications. We focus on the effects of the dynamic gate control, the 4-phase gate-boosting and cross-coupled configuration for enhancing the performance of the charge pump circuits. Several different charge pumps operated under different working conditions are then investigated in detail. © 2011 Elsevier Ltd. All rights reserved.