The Design Of A Synchronous Step-down DC/DC Switching Power Supply Management IC

With the rapid development of the switching power supply technology, the DC/DC switching power supply IC has already obtained the widespread application in domains such as communication, computer, and consumptive electronics. In recent years, the demand of portable equipment with battery power supply expands more and more quickly, so does the the DC/DC switching power supply IC. What is more, it requires its performance to become better and better. In order to adapt to the application requirement of portable electronic products, based on the 0.6μm BiCMOS process, the paper designs a synchronous step-down DC/DC switching power supply management IC by using the EDA tools Pspice.The IC this paper designs has enabling control function, working with PWM modulation. While achieving a higher switching frequency, it can also ensure higher conversion efficiency either the circuit has heavy or light load. In order to eliminate the impact of the inrush current and lower the input capacitance value, the circuit has soft-start control function. Over current situation is avoided by current-limiting protection circuits, also, this IC has over temperature protection and undervoltage lockout function. That means when the circuit suddenly has faults such as over temperature or undervoltage, the whole circuit will shutdown automatically until the faults are eliminated. By using the tools of Hspice, every sub-circuit and the whole circuit are simulated, and the results show that this IC works stably and every indicator achieves the design requirement. The PWM switching frequency reaches 2.439MHz. The input voltage range is 2.7V-5.5V, and the output voltage can be changed from 0.6V to 2.5V. The conversion efficiency reaches 81.5%.From above on, this DC/DC switching power supply management IC uses synchronous rectification technology, which improves efficiency and omits the external schottky diodes used in conventional step-down switching power supply management IC. It can be used in applications priority to consider both of small size and high efficiency, because it allows users to sacrifice part of efficiency in exchange for smaller external components.At the end, this paper positions the whole circuit layout. Then it designs the layout for some module circuit and checks it by using Cadence Virtuoso and Cadence Dracula. Considering the layout and the function of the whole circuit, this IC meets the requirement of small package, and it can be applicated in mobile phones, PDAs, MP3 players and other portable electronic products.