The Design And Study Of Dual-Loop Dynamic Compensate Low Dropout (LDO) Regulator

Along with swift development in electronic technology, there comes an urgent need for high-power system which generates supply voltage for portable electronic products. LDO linear voltage regulator is widely used in Lithium battery charging and low voltage digital supply circuits, for its advantages of simple construction, small area, low noise and high inhibition of ripple, etc. Better system stability and faster load transient response are required to meet the needs of power market development. This thesis will provide a dual-loop LDO with low voltage, low power dissipation and fast transient performance.This thesis will firstly provide a brief review on a recently research in power management ICs and introduce some basic knowledge and basic indicators of LDO. Then the key points of LDO design and various trade-offs will be expounded, critical skills and improvements also discussed in allusion to the parameter design. Among those, certain issues will be emphasized, including the influence of dual-loop structure on system stability, the accelerating of transient response by positive feedback, improvements of circuit's load capacity by back gate control and improvements of lowest dropout voltage, etc. Then two schemes to improve the band gap circuit will be proposed, in which an effective way to restrain the influence of reference voltage induced by current mismatch and an implement of second order exponential compensation are involved. Finally, the whole circuit construction has been proposed, and some main circuits will have also been designed out. The results of simulations and analysis have been shown in detail.This LDO is designed on the basis of 0.6μm BICMOS process, and its performance has been verified by Hspice simulation. The minimal dropout voltage is 223 mV, maximum output current is 320 mA and the quiescent current is 25μA. Properties as liner regulation of 0.14% and load regulation of 0.45% are achieved. The overall simulation results shows that better performance of LDO have been realized fully.