Design And Application Of Low Voltage CMOS Charge Pump

Charge pump circuits that make use of charge accumulation in the capacitor can pump charge upward to produce voltage higher than the regular supply voltage, and they are widely used in memory circuits, such as Flash Memory, for the programming and erasing of the floating-gate devices. At the same time, charge pump circuits are also used in the low-supply-voltage switched-capacitor systems that require high voltage to drive the analog switches and dc-to-dc converters and so forth.Recent development of portable mixed-mode communication systems have brought low voltage and low power consumption to be a tendency for circuit design, so the supply voltage falls continuously. When the supply voltage is reduced to a level, such as IV, the analog MOS switch will not operate adequately. In order to overcome this problem, constructing the high performance charge pump circuits is essential for low voltage analog circuit design.In conventional CMOS charge pump circuits, the pumping high voltage is limited by MOS threshold voltage, so that it can not use less cascade stages to pull up a high voltage which we want to generate. Especially in CMOS N-well integrated circuits technology, the body effect will cause the NMOS threshold voltage following the pumping voltage to be lifted and then the highest pumping voltage will be limited. Therefore, a four-phase charge pump circuit is invented to surmount this problem, but the current loading capability of this circuit is unfavorable and the driving clocks must have four-phase non-overlapped "signals.This thesis firstly makes a detailed analysis and expatiation for several conventional charge pump circuits, and then proposes a new two-phase charge pump, and analyzes its structure and operational principle. And the simulations of several charge pump circuits including the new two-phase charge pump circuit are compared, the result indicates that the new charge pump overcomes the shortcomings of the conventional circuits and has the better performance. Furthermore, based on the proposed new charge pump circuit, a IV to 3.3V high voltage generator which is used in analog switch circuit and a 3V to 10V high voltage generator which is applied to EEPROM or Flash memory are designed, the components and design thought of two high voltage generators are also discussed in detail. And the simulations of two high voltage generators are accomplished by TSMC 0.18uW CMOS technology (T018U), the outcome testifies that two highvoltage generators that take the new charge pump as the core circuit have the higher performance.