A 233-MHz 80%-87% efficient four-phase DC-DC converter utilizing air-core inductors on

Abstract—We demonstrate an integrated buck dc–dc converter for multi-CC microprocessors. At nominal conditions, the con-verter produces a 0.9-V output from a 1.2-V input. The circuit was implemented in a 90-nm CMOS technology. By operating at high switching frequency of 100 to 317 MHz with four-phase topology and fast hysteretic control, we reduced inductor and capacitor sizes by three orders of magnitude compared to previously published dc–dc converters. This eliminated the need for the inductor mag-netic core and enabled integration of the output decoupling capac-itor on-chip. The converter achieves 80%–87 % efficiency and 10% peak-to-peak output noise for a 0.3-A output current and 2.5-nF decoupling capacitance. A forward body bias of 500 mV applied to PMOS transistors in the bridge improves efficiency by 0.5%–1%. Index Terms—Buck converter, CMOS, dc–dc converter. I