一种双路USB功率开关的设计

【作者】 徐建华；

【导师】 罗萍；

【作者基本信息】 电子科技大学 ， 微电子学与固体电子学， 2005， 硕士

【摘要】 USB(Universal Serial Bus)是一种新型的总线标准,凭借其即插即用、接口可扩展等优点而得到了迅速普及。一个USB 系统能否可靠工作需要很多条件,其中最重要的一条就是要有合格的电源管理。本文的研究对象就是USB 电源管理系统中的关键元件——USB 功率开关(USB Power Switch),本文成功设计了一款完全符合USB2.0 工业规范[1]的双路USB 功率开关。USB2.0 规范发布于2000 年4 月,相对于其之前版本的主要改进是大幅提高了USB 的传输速率,在电源管理方面的要求也有相应的变化。本文在预先设定电路功能和指标时,完全遵守USB2.0 的规定。在功能设计上,不仅具有限流、电源切换和故障报告等基本功能,还具有软启动、1ms 故障信号延时、过温保护、欠压锁定等增强功能。本文设计的芯片有效输入电压为2.7V～5.5V,最大工作电流为200μA,最大导通电阻为140m?,连续电流输出能力为500mA 以上,典型的限流值设定在1A,欠压锁定的阈值为1.8V。在电路设计时,先根据整体的功能设计把电路分为12 个子电路,接着为每块子电路定义功能和指标,之后按照这些功能和指标搭建各个子电路。搭建子电路时,本文采用人工设计和EDA 软件辅助相结合的方法,所有电路都经过详细推导和演算,并用电路仿真工具HSPICE 进行验证。在整体电路仿真时,考虑了芯片各种可能的应用环境(如输出短路,电源突降等情况),逐一进行功能验证。本文第二章阐述了整体电路的工作原理;第三章有重点地对若干子电路进行了详细分析,并给出了仿真结果;第四章给出了整体仿真的一些重要波形。由于篇幅有限,文章只对作者重点参与的子电路进行了详细分析,对于其他子电路只作了简单的功能介绍。通过详细的电路分析,加之有力的仿真数据,有理由认为笔者完全达到了既定设计目标,成功设计了一款双路USB 限流开关。随着USB 的迅速普及,USB 功率开关的应用也将越来越广泛,对产品的设计要求也将不断提高。国外的很多半导体公司都已经推出了各自的USB 功率开关产品,如Micrel 公司的MIC2026、MIC2526、Maxim 公司的MAX1922、MAX1930。但是国内在这方面的研究相对较少,因此,本文所做的工作具有一定的学术和经济意义。更多还原

【Abstract】 Universal Serial Bus (USB) is an emerging standard for data transmission. With its “Plug and Play”feature and port expansion feature, USB is becoming more and more widely used. Choosing the right power management strategy is essential to a USB system which functions well. This thesis is about the USB power switche, which is a crucial device in USB power management systems. A dual channel USB power switch is successfully designed in this thesis. USB Specification 2.0, released in April 2000, has much higher data transmission speed comparing to its former edition. Corresponding changes also can be seen in chapters about power management. In this design, function definitions and parameter presettings are fully compliant with USB 2.0 specifications. The designed chip not only has basic functions such as current limiting, switching and fault flag, but also has enhanced functions such as soft start, 1ms fault flag delay, over temperature shutdown and under voltage lockout. Critical device parameters are also presetted carefully. The supply voltage range is 2.7V-5.5V, the maximum operating current is 200μA, and the maximum on resistance is 140 m?. The chip guarantees a continuous output current of 500mA while limits the current to no more than 1A typically. The under voltage lockout threshold is about 1.8V. When building the circuits, twelve function blocks are defined according to the whole chip function, and then functions and parameters of each block are defined before they are embodied with practical circuits. All sub-circuits are derived carefully and verified by HSPICE. In whole chip simulation, all possible application situations, such as shorted output and under voltage, are well simulated and verified. In chapter 2, the overall working principles are introduced. Chapter 3 deeply analyzes several sub-circuits and gives their simulation results. Chapter 4 is some important curves of the whole chip simulation. Those sub-circuits which are designed mainly by the author are particularly analyzed, and simple introduction is given about other sub-circuits. Circuit analysis and simulation results show that the design has been successfully completed.更多还原