Research And Design Of Protection Circuit In USB Power Management Chip

Because of its advantages of support hot plug, fast transfer rate and convenient carrying, the Universal Serial Bus (USB) interface is fast gaining popularity in recent years. With the progress of science and technology, the USB 3.0 has higher transmission rate, can provide greater power and more output current. New intelligent products on the market are mostly adopts USB communication and charging. However, in order to deal with some of the harsh environment and emergency in the process of using, how to design a safe and reliable USB power management chip is a difficult problem that engineers have to face. From the point of view of safety and reliability of the chip, the design of the protection circuit of USB power management chip is focused on. Through simulation and verification, the design of the current limiting protection circuit, thermal-shutdown circuit and abnormal alarm circuit are completed.First,the research status and development trend of protection circuit in USB power management chip, as well as the important performance parameters of USB power management chip are introducred briefly. At the same time, the principle of architecture of the USB power management chip is expounded in detail, the working process of current limiting protection circuit and thermal-shutdown circuit is analysed. Resistance detection and SENSEFETs detection are used to monitor the system current in this paper.Then, the design process of current limiting protection circuit, thermal-shutdown circuit and abnormal alarm circuit are introduced in detail. The system can’t be effectively protected with the traditional current limiting protection circuit in short trouble. A double threshold cuttent limiting protection circuit is presented. When the system is over cuttent, it output constant cuttent and when the system is short circuit, the constant current source output is reduced to a lower threshold. The temperature monitoring and thermal-shutdown function is realized by comparing the reference voltage of the bandgap with the emitter base voltage of the PNP transistor. If the system is overload, short circuit or over temperature and other abnormal conditions, it will output abnormal alarm signal to the USB controller.Finally, based on 0.25um BCD UMC technology, Cadence and Hspice software are used to circuit simulation. Simulation results show that the over-cuttent threshold is 2.5A and short-current threshold is 1.6A. The rising threshold of the thermal-shutdown circuit is 130℃, and the falling threshold is 100℃, it has the hysteresis temperature of 30 ℃, and abnormal alarm signal has 12 ms delay. All the indexes meet the design requirements, and it has high application value in USB power management chip.