An Improved Current-Mode CMOS DC-DC Buck Converter with Rail-to-Rail Current-Sensing Technique

An innovative current-mode DC-DC Buck Converter is presented by this paper, integrated with power switches and a novel on-chip current-sensing circuit for the feedback control loop. The proposed current-sensing circuit, consisting of a deep negative feedback loop and a series of controlling switches, accurately senses the ramp-up portion of the inductor current thus yields a precise sensing-voltage. The feedback loop is implemented with a Rail-to-Rail Amplifier, together with a Common-Source stage with source degeneration. The DC-DC converter is simulated under SMIC 0.13um CMOS process. This converter operates with a supply voltage of 3.3V, and the operating frequency is 1MHz. The experimental and simulation results show that the output ripple voltage is about 2mV with a 50uF off-chip capacitor and a 1uH off-chip inductor, which is less than 0.2% of the output DC voltage.