Design Of Synchronous Buck DC/DC And LDO Dual Controller XDJ6379 IC

With the developments of electronics and telecommunication, portable electronical products become more and more popular. The developments of power management technologies and applications are rapidly promoted. Especially along with the trend of developing smaller, digitized and multifunctional semiconductor products, the status of integrated voltage regulators is more and more important.Based on the project of the Institute of Electronic CAD,"Theoretical research and design of key technique for power management IC", a synchronous Buck DC/DC and LDO dual controller named XDJ6379 is designed in this paper.In this paper, the design of XDJ6379 is described in detail, including definition of the IC specification, further analysis of the electrical characteristics, implements of subsystem circuits and simulation of the whole chip. XDJ6379 integrates both the large current and high efficiency Buck PWM controller, and the low current and low noise linear regulation controller. So it is the ideal supply for high-performance graphics cards, IA equipments etc. This paper makes deep reserch and calculation to the system stability of voltage-mode PWM DC/DC controller, and puts forwards a scheme of internal frequency compensation circuit which can be integrated inside the chip to replace the external RC compensation network of the chip. By using the synchronous switch to substitute the Schottky diodes, the efficiency of the chip has been enhanced greatly. The advanced design of soft-start and fault logic circuits controls the time sequence strictly, so the stability and reliability of the system are improved largely, and prevent surge current from power supply input during power on. In addition, lots of protection circuits are integrated in the chip, such as thermal shutdown, over voltage protection, under voltage lockout, over current protection, and so on.XDJ6379 is designed based on 0.6μm BCD process, and is verified by Hspice. According to the simulation results, its function and performance can meet the design requirements.