High efficiency, inductorless step-down DC/DC converter

A high efficiency, inductorless step-down DC/DC converter is proposed. High efficiency is achieved through the combination of the fractional conversion ratio charge pump and load current sensing circuit. The circuits have been designed in the TSMC 0.25mum 2.5V/5V mixed signal CMOS process. The DC/DC converter has an output voltage of 1.8V (load current les 200mA) with the accuracy of plusmn 1% and the ripple voltage less than plusmn10mV for the input battery voltage from 2.8V to 5V. The peak and average efficiency is over 85% and 65%, respectively