For The Usb Interface Power Management Chip

Interface is becoming one of the important parts of computer system to connectthe real world and used widely. People are focusing on how to enhance the interfaceperformance to meet the technology development. The interface technology isimproved ceaselessly nowadays. USB not only has the merits of the commoninterface technology, but also has some especial performance such as supplyingpower and bearing hot-plug, this technology has become one of the most importantinterface technology in the world. National, MAXIM, TI and some other famouscompanies have much experience on the technology, but native companies pay moreattention to the USB controller parts rather than power management performance.USB power switch in this paper is based on protocol 2.0. The developmentbackground, applications, the critical electronic characteristics and advantages of theUSB power switch are introduced in the beginning of this paper. Some of theimportant sub blocks such as current limit, overheat protection, logical control andsoft start are mostly discussed in the next place. This paper presents a new approachof internal current limit circuit by using adjustable current source instead of a SENSEresistor, and describes the method of the design. The feasibility and advantages of subblocks is proved via HSPICE subsequently. Author gives whole chip simulationperformance and data after front design. Finally, the summarization of this design ismentioned and some experience is given in the end of this article. Moreover, authoranalyses the future of USB system.The paper makes a conclusion of USB power switch design through the circuitanalysis, simulation, and calculation. It gives out some experience on analog ICdesign.