A fully-integrated 0.18μm CMOS DC-DC step-down converter, using a bondwire spiral inductor

A fully-integrated DC-DC step-down converter in a 0.18 mum 1.8 V CMOS technology is realized, with a bondwire spiral inductor and integrated MOS and MIM capacitors. The converter is designed to generate an output voltage of 1.8 V out of a 3.6 V power supply. No external components are required. The maximum power conversion efficiency is 65 %, for a voltage conversion ratio of 0.5. This is a 23 % improvement compared to a linear regulator. Higher values are likely to be reached using a converter with external components, which is not the case here. Stacked transistors are used to cope with the high voltage. A novel control system based on a constant on/off-time keeps the output voltage constant at load conditions from 0 mW to 300 mW. The converter operates in discontinuous, asynchronous switching mode. The switching frequency ranges from 20 Hz to 140 MHz.