A Fully-Integrated Switched-Capacitor Step-Down DC-DC Converter With Digital Capacitance Modulation in 45 nm CMOS

Abstract

Implementing efficient and cost-effective power regulation schemes for battery-powered mixed-signal SoCs is a key focus in integrated circuit design. This paper presents a fully-integrated switched-capacitor DC-DC converter in 45 nm digital CMOS technology. The proposed implementation uses digital capacitance modulation instead of traditional PFM and PWM control methods to maintain regulation against load current changes. This technique preserves constant frequency switching while also scaling switching and bottom-plate losses with changes in load current. Therefore, high efficiency can be achieved across different load current levels while maintaining a predictable switching noise behavior. The converter occupies only 0.16 mm2, and operates from 1.8 V input. It delivers a programmable sub-1 V power supply with efficiency as high as 69% and load current between 100 μA and 8 mA. Measurement results confirm the theoretical basis of the proposed design.