Research And Design Of Charge Pump For Flash

In the current electronic product market,Flash is widely used in portable electronic devices.The working mechanism of the Flash to store data mainly needs to be realized by the channel hot electron injection effect(CHEI)and the quantum tunneling effect(FNEI),which requires high voltage to realize.Because Flash uses a single power supply,and considering the voltage of power supply needs to be low and the size of it needs to be small,it is necessary to design a high-voltage module inside Flash to provide the high voltage for CHEI and FNEI.The charge pump circuit is the primary choice for the internal boost module of Flash due to its small area and no need for inductance.Based on the application requirements,this paper has realized a boost system applied in Flash.First,according to the basic working principle,equivalent circuit model and specifications of the charge pump,the performance is optimized in two aspects:structure and design parameters.Considering the application requirements of Flash.Firstly,a cross-coupling structure is adopted to ensure supply power to the load during each cycle,thereby reducing the voltage ripple and increasing rising speed of the voltage.To solve the problem of threshold voltage loss in traditional charge pump structure,a dynamic biasing of the gate is adopted to keep the transistors in the linear region,which can eliminate the threshold voltage loss and improves efficiency when the transistors operate;to avoid the influence of the body effect,this paper adopts dynamic biasing of the substrate to make sure the substrate of the PMOS biased at a higher potential on both sides of the circuit.In order to improve the shortcomings of the simple ring OSC,a current-controlled OSC is used to generate a more stable clock signal.Then,according to the timing requirements of the charge pump,adopt the four-phase non-overlapping clock.In order to reduce the ripple generated in SKIP mode,a faster,larger gain regenerative comparator is used to detect smaller voltage differences and generate a faster control voltage.Finally,to ensure the stability of the voltage compare,the second-order temperature-compensated bandgap is used as a reference source to further reduce the temperature dependence of the voltage compated.Finally,according to the connection feedback relationship of the system,the overall circuit is simulated to verify the integrity of its function.Based on the HG 0.35?m process at different corners,the temperature range is-40?-125?.Within the power supply voltage range of 3.0V-3.7V,and load current range of 0-100?A,the overall simulation results show that the output of the system is about 9.0V,and the voltage ripple is controlled within 120m V,the layout area is about 0.25 mm~2 and within 5?s the voltage can be raised to 90%of the required voltage to meet the programming and erasing requirements in Flash.