The Pfm And Efficient Low-voltage Low-power Boost Converter Design

Now, more and more electronic equipments are portable and multifunctional, which make the DC/DC converters must have special properties, such as high efficiency, low quiescent current, small board space and low cost. In order to ensure the system work stabilization, the modern electronic products often use the DC-DC converters to provide the voltage.PFM and boost operation principle and a high efficiency synchronous step-up DC-DC converter with wide input supply voltage and multi output versions, which uses 0.5μm standard CMOS technology, are presented in this paper. The input supply voltage ranges from 1.1V to 5.5V and according to the different connection methods of FB port, its output versions include 3.3V, 5V and 1.8V to 5.5V. The typical ground current (quiescent current) is 35uA at 200mA load, and less than 0.1μA in shutdown mode. This converter include a build-in synchronous rectifier, with the advantage of small positive overdrive voltage, high interdiction voltage and small countercurrent, avoid using the outside SBD, it can minish the power waste and upgrade the efficiency effectively. The high switching frequency allows the use of small surface-mount capacitors, saving board space and reducing cost. It also includes hysteresis and current limit, protecting the load and the regulator during fault conditions.First of all, the whole chip function diagram is designed after analyzing the principle of PFM boost DC-DC converter and the system required function. And then, the sub-block circuit is designed according to the whole chip function and structure. In sub-block circuit section, the typical circuits including FB comparator block, hysteresis comparator block and current-limit block are introduced. The basic principle and main parameters of every sub-block circuit are noted and the corner simulation results are given at the end of each segment.Based on the principle analysis and circuit design of PFM boost converter in the beginning chapters, the whole chip corner simulation results done by HSPICE EDA tool verified that the IC has achieved the expectations, both functions and electrical characteristics.