Design Of Line Switch XD3500 With Low Dropout

With the rapid development of information technology, the status of the power supply technology is becoming increasingly important. Power technology in the computer wireless communications equipment, automotive electronics or other fields is widely used. Especially now that the rapid development of portable electronic devices, making the power management chips market become the focus attention of the electronics field. And power management chips are proposed higher requirements, such as low cost, low power, high efficiency, and high reliability and so on. However, in all kinds of power management chips, line switch chips have a pivotal role. Most of the monitors, portable devices and laptops need to have a line power switch, and its basic function is to provide an external power supply to the system. Line switch chips can be used to control the inrush current, the power-up sequence control, power isolation or used as a simple power switch. From these applications we can see that line switch chips need to have features such as output voltage equal to the input voltage, over-current protection, and low static power consumption and so on.In this paper, on the base of a detailed study on the basic principles of traditional line switch chips, a low dropout line switch IC XD3500 is designed. This chip is mainly used for displays, tablet PCs and other portable devices. The works, advantages and disadvantages of traditional line witch chips are introduced in this paper, and for its lack of over-temperature protection and current limiting functions, the structure design and circuits of XD3500 are presented. In addition, XD3500 also has functions like soft start, undervoltage lockout and fast current limiting.The manufacturing processes and layout design of integrated circuits are researched in this paper. With the use of Cadence software, each module circuits are specially designed and simulated, and the design and simulation of overall circuit of XD3500 are completed. Then, on the base of 0.35?m BCD process, the overall layout of XD3500 is completed, and final tapeout successfully. Finally, the various parameters and functions of the chip are tested in detail, and test results show the good performance of the chip, which meet the needs of practical applications.