Design Of A Low Dropout Linear Regulator WithBackup Supply Switching

With the progress of integrated circuit technology, power management chip market has been a good development, the ability to achieve stable and efficient power management, will affect the overall performance of the electronic products. LDO linear regulator with its simple structure, low cost, low noise, etc can be applied in electronic products, especially for battery-powered portable electronic system, LDO linear regulator is worth choosing one of the power management schemes.This thesis is designed with a high performance dual step-down switching regulator chip LDO linear regulator, which main function is to offer power supply to an external NMOS gate drive circuit and most of circuit in chip. The chip provides two independent LDO, according to the voltage value of a pin to decide one of the LDO work, another LDO closed, specifically the internal chip circuit is powered by chip input power supply or backup power, One LDO voltage mode provides to 5.25 V, the other can provide voltage to 7.5V, this can minimize the power consumption. The entire circuit contains Bandgap Reference, Error Amplifier, Pass Element, Feedback Loops and other circuits, the thesis analyzes the important sub-circuit designs in detail.The circuit design is based on CSMC 0.5um BCD process, and uses Spectre simulation, considering the input supply voltage(4V ~ 36V) changes, temperature(-55 ℃ ~ 125 ℃) and process corners(SS, TT, FF), and ultimately simulation results show that the sub-circuit and the whole circuit have reached the design requirements. Among them,wide input supply range of(4V ~ 36V) can be adapted to all battery chemistries.Finally, using the Virtuoso Layout Editor of Cadence, complete the layout of the whole design, and achieve DRC and LVS verification.