Research And Design Of Low Dropout Linear Regulator

Low-dropout(LDO) linear regulator is a DC linear regulator whose input voltage is larger than output voltage. It owns low power, external circuit is simple, low output noise, high PSRR, fast input/output respome, small size and low cost. Therefore it is applied broadly in automobile electronic equipments, portable communications equipments, industrial and medical fields. It has a large anticipated market. There is great significant to carry out this paper.The topology of the system and the basic princibles of the system are researched and analyzed in this paper firstly. The key technologies of system implementation are introduced. In order to perfect the function of the system, over temperature protection and over current protection functional modules are introduced to protect the system. Then, the circuit level design of the modules is introduced detailedly. The key modules mainly contain error amplifier, bandgap voltage reference, overcurrent protection circuit, overheat protection circuit.The system is designed in CSMC 0.5μm CMOS technology, and simulated by the Spectre of Cadence Company. The simulation results show that the range of input voltage is from 2.67V~5V and the stable output voltage is 2.5V, the Dropout voltage voltage is 170mV while the largest load current is 150mA, the quiescent current is about 55 ? A, the power supply rejection ratio(PSRR)is about 66dB. In addition, when the temperature is above 117o , the overheat protection circuit begin to work. When the output current is greater than 200mA, the overcurrent protection circuit begin to work. This ensures the safety of the circuit. It can clearly be seen that the designed LDO linear regulator has a good overall performance. After circuit design is completed, the layout of this chip is designed on Virtuoso integrated in Cadence.