Research And Design Of An Efficient Synchronous Buck DC-DC Converter XD38873

Since entering in twenty-first Century, with the development of society, new technology has developed rapidly. Which has greatly facilitated people's lives. people's pursuit of quality life becoming more and more high. This has promoted the rapid development of portable electronic products market. Switching power supply with high efficiency, low cost and high integration has become the main structure of portable electronic products. Based on this background, a high efficiency synchronous buck DC-DC converter chip XD38873 is designed.This thesis first introduces the significance of this research, the development of power management IC and its future development trend. Then the basic theory of DC-DC converter is introduced, including three kinds of topology and principle analysis. Since the XD38873 is a buck converter, the subsequent analysis of the Buck DC-DC converter is done, and the synchronous rectification technology and the slope compensation technology are introduced. Subsequently, the electrical characteristics and system structure of the chip XD38873 are analyzed. The selection of the main components of the chip is introduced in detail. And then give the design principle analysis, simulation and verification of the chip. Finally, the layout design of XD38873 chip is introduced, and the simulation analysis of the whole circuit is finished.The high efficiency synchronous Buck DC-DC converter designed in this paper uses Synchronous rectification technology. In this chip, the continuous flow tube using MOS tube replaced the previous Schottky diode. Then, the problem of low efficiency of DC-DC converter in the light load case can be effectively solved. In this way, the maximum efficiency can reach 95%. The chip XD38873 uses frequency conversion technology in load abnormal. In the oscillator module, the detection circuit is added to detect the change of the output signal, once the chip is in a short circuit or overload, the judge circuit will work to reduce the frequency of the system in time. At the same time, the chip in the short circuit, may trigger the HICCUP mode, then the chip will be protected until the exception removal. Chip XD38873 EN pin multiplexing technology, through the EN pin can control the chip enable to switch, can also be synchronized with the external clock signal. Then through this way the application of the chip can be expanded in large extent. The chip is provided with a soft start module, which prevents the chip in the starting process of the surge current and the overshoot voltage of the system. XD38873 converter chip has its own PG(Power Good) module, you can indicate whether the power supply is enough. once the battery is insufficient, the chip can give instructions to the user. The chip have many protection modules, such as over current, over voltage, short circuit, over zero, over temperature. which ensure the reliability and safety.The overall design of the circuit is based on 0.5 ?m BCD process, We use Cadence to simulate and verify the chip. The simulation results show that the chip can meet the design requirements and the chip can performance stability. Based on the design and verification of the above, the layout of the chip XD38873 is designed. Chip layout design is very important to ensure that the design of the function can be truly realized.