Automatic L / Buck 50ma Switched Capacitor Charge Pump 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, low weight and low cost. The inductive DC/DC converter is the traditional approach for power management. But with the development of sub-micron technologies and the use of high value multi layer ceramic capacitors, the efficiency of charge pump is improved which make charge pumps are still widely used not only in light load application but also in higher output currents condition.Charge pump operation principle and a 50mA Switched-Capacitor Automatic Step-up/Step-down Charge Pump 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 range is 2V to 5.5V and its output versions include 2.5V, 2.7V, 3V, 3.3V and 5V. The typical ground current (quiescent current) is 1mA at full load, 60μA with no load and, and less than 1μA in shutdown mode. The input supply voltage may vary above or below the output voltage and the output will remain in regulation by automatically selecting step-up or step-down operation mode. It works well for step-up or step-down without the need for inductor, providing low EMI DC/DC conversion. The high switching frequency allows the use of small surface-mount capacitors, saving board space and reducing cost. It also includes thermal protection and current limit, protecting the load and the regulator during fault conditions. The efficiency is very high, especially under low load condition, because the output voltage is regulated by skipping clock cycles as necessary.First of all, the whole chip function diagram is designed after analyzing the principle of charge pump and the system required function. And then, the sub-block circuit is designed according to the whole chip function and structure. In the charge pump principle section, the principle of linear mode and skip mode are analyzed in detail. The principle of step-up/step-down and the main parameters are also given in there. In sub-block circuit section, the typical circuits including reference, operational amplifier,thermal protection and current limit are introduced. The basic principle and main parameters of every sub-block circuit are noted and the simulation results are given at the end of each segment.Based on the charge pump principle analysis and circuit design in the beginning chapters,...