The Design Of CMOS Regulator

The application of portable electronic equipment, such as mobile telephone, MP3 player, is becoming more and more popular. They are all battery-driven. The output voltage of a battery will decrease sharply as time passes. With the development of VLSI technologies, more and more transistors and circuitry can be integrated in a chip, while different circuitry needs different power supply and special performance of power supply. In addition, the mobile electronic equipment will burn up under some unexpected conditions , for example, the user makes a short circuit carelessly, or connects the battery with incorrectly polarity. Thus we should provide the stable, special and well protected voltage to the system to make the equipment work normally. So there should be an extra circuitry to supply power for the system.This paper presents a practical design of voltage regulator according to the need of the application. The schematics includes four parts: bandgap reference voltage and reference current, 2.7V and 1.8V regulator, over-load protection , Low Battery Detection (LBD) .The design of bandgap , seeks a tradeoff between the output voltage change due to temperature change(-40oC~80oC) and output voltage change due to supply variation(2.9V~5V) , and generates an output that is stable with less than 1mV of variation;Using the tunable resistors, we can stabilize the change of bandgap output voltage resulting from process fluctuation effectively. 2.7 volt voltage regulator use highly efficient voltage pump, and minimizes the drop-out voltage, achieves a balance among stable time, ripple, power consumption and the area the circuits needed. This paper designs an over-load protection circuits as well, it will work automatically when there is a over-load, and this can protect the system from potential damages. A programmable low battery detection circuits is designed also. It can decide which voltage is the lowest voltage the system allowed via MCU program. It is convenient and flexible and can effectively prevent the low voltage damage to the system. The whole system uses 0.18um process of SMIC(Semiconductor Manufacture of International corporation). Simulation indicates the whole system performance is fine. It can fully meets the requirements of desired system.