Research And Design Of A Synchronous Buck DC-DC Converter XD2825 With High Efficiency And Programmable Frequency

With the continuous development of electronic science and technology, portable electronic equipment is becoming more and more common, also the requirement of the performance is becoming more and more important, as the performance of the power supply is an important factor to portable electronic equipment performance, the research of high performance power management chip is of practical application significance. In this paper, a kind of efficient synchronous BUCK DC-DC converter XD2825 with adjustable frequency is designed based on CAD institute’s scientific research project “Research and Design of Power Management IC’s Key Technology Theory” of Xidian University.Through learning and understanding the basic theory of design of analog CMOS Integrated Circuits, and combining with the current power equipment market demand, the converter chip XD2825 adopts PWM modulation method of peak current mode control loop, it has faster transient response speed, and uses synchronous rectifier technology to effectively improve the conversion efficiency of the system. To expand the application of chip XD2825, the system has integrated a clock frequency synchronization module to adjust outside frequency, so that the chip XD2825 can work under a wide range of clock frequency. To make the system has a high conversion efficiency in all range of the load, so integrated the low power mode, the system can accord to the different load adoptes continuous work mode or discontinuous work mode.This paper will first introduce the research background, present status and the development of power management IC, and the main performance index of switching power supply; And then it analyzes BUCK DC-DC converter’s working principle, including DC-DC converter topology structure, main working mode, main modulation method and main control mode, which provides a theory basis for the Systerm-level design of XD2825. Then we will research and design the chip XD2825 to the system level, determine the function and the electrical characteristics of the index of the chip XD2825, and describe the overall functional block diagram of system and each function module in detail; Finally to the whole simulation of chip XD2825, verify its functionality, and after a brief introduction to the design of landscape technology, presenting the landscape layout and the overall layout of the chip XD2825.The chip XD2825 which uses 0.5μm BCD 30 V process technology, relies on the Cadence Spectre simulation tools for the whole simulation validation. The chip XD2825 has a wide range input voltage from 4.75 V to 20 V, internal fixed clock frequency of 500 KHz, external synchronous frequency from 300 KHz to 2MHz, maximum load current of 4A, and the conversion efficiency can reach 95%. This chip can be widely used in the router, such as notebook computers and mobile power supply equipment, with high conversion efficiency, low static power consumption and stable work, etc, which will greatly improve the power of the portable electronic equipment performance.