Research And Design Of A Ldo Linear Regulator

With the rapid development of microelectronics technology, low-dropout voltage and linear regulators (LDO) as the popular power regulators make it the hotspot in the field of electronics in recent years, due to its incomparable advantages, such as low consumption, relatively simply external circuit, low noise, small volume of the chip, high PSRR.The paper researches and designs a new LDO with a variety of voltage output based on CSMC CMOS 0.5um models. LDO mainly includes the Reference voltages module, the feedback resistance network and adjustment transistor, the error amp module, and join the trimming resistors, thermal shutoff module, Short circuit and current limiting protection module. The error amp designed in this paper adopt two-stage structure, the first stage is folded cascode operational amplifiers, the second is the push-pull output, to get the enough phase margin by using Miller compensation; when designning the trimming circuit, join the resistance to the branch of the drain of adjustment transistor to obtain different output voltage; thermal shutoff module is designed by adding device for producing the Hysteresis effects to avoid concussion phenomenon; in the Short circuit and Over current protection module designning, comparing constant voltage with the voltage whose current produced through mirroring to the current of PMOS, and the results to be the adjust signal, at same time, the results from comparing the output voltage with a particular voltage will to be the limiting signal,. in order to realize the high reliability and high stability.This paper Simulates all modules and the whole circuit using HSPICE simulation software, the results show that the band-gap reference voltage is about 1.248V,which has good temperature characteristics and high PSRR; thermal shutoff module shuts the circuit off when the temperature gets to 142 degrees, and restart the circuit when the temperature drops gradually at 112 degrees, the Hysteresis temperature is 30 degrees; over-current protection circuit start working when load current is 816mA,short circuit protection circuit start working when output voltage smaller than 0.7V; the output voltage can vary from 3V to 4.5V; the Sv and SL of LDO both meet the requirements.At last, design the layout of LDO under consideration of device matching,Floor planning and a series of elements; and through the DRC, ERC, LVS to ensure the layout designed is correct.