The Research Of Charge Pump System Applied To Embedded Flash

Flash memory is now dominating the non-volatile memory family. It has beenwidely used in portable electronic devices for a couple of decades. High voltages arerequired to program and erase the flash memory cells based on two mainmechanisms:channel hot electron (CHE) injection and Fowler-Nordheim (FN) tunneling.Charge pump is an indispensable component in flash memory systems in order togenerate high operation voltages for programming flash memory cells.Charge pump is a kind of DC-DC converter which consists of capacitors and aswitch network only that can be fully integrated on silicon. In this paper, at first，wereview some different types of charge pump circuits. Then we focus on the conventiona lDickson charge pump circuit and analyse the characteristics of steady state and dynamicstate of charge pump.We also get the theoretical derivation of the basic formula of thecharge pump circuit including output voltage, rise time and so on.In accordance with the Flash system, we designs a charge pump system based onthe four phase charge pump circuit, including the charge pump circuit, oscillator, fourphase clock generator circuit., comparators and regulators. Then we finishes thesimulations of sub-circuits, as well as the charge pump system, The result indicates thatthe charge pump operates normally and that all performances meet the designrequirement. In order to enhance the efficiency of the charge pump circuit, we designsanother charge pump based on the cross-coupled voltage doubler. Then we make acomparison simulation on output voltage and efficiency between the four phase chargepump and cross-coupled voltage doubler.At last, we use the GSMC0.13μm CMOS process to implement the charge pumpsystem based on the four phase charge pump, and then gives the layout of the wholeFlash system.