A noise-shaped switched-capacitor DC-DC voltage regulator

This paper presents a delta-sigma control loop for a buck-boost dc-dc converter with fractional gains. The charge pump used to convert the input voltage acts as a D/A converter in the loop, and its output ripple is frequency shaped by the loop, which also provides the pulse-frequency modulation needed for the conversion. A test chip realised in a 0.72-µm CMOS process and clocked at 1MHz provided suppression of tones up to 50dB in the 0-500kHz range. The target output voltage may be from 1.8V to 4V for loads up to 150mA. The input voltage range is 3V to 5V.