A 78%-efficiency li-ion-compatible fully-integrated modified 4-level converter with 0.01–40mW DCM-operation in 28nm FDSOI

This paper presents a battery-connected DC-DC converter integrated in a scaled CMOS process. To achieve high efficiency while blocking the 2.8–4.2V Li-ion battery voltage range using only 1.5V transistors, a modified 4-level buck converter is proposed. Implemented in 28nm FDSOI, the converter switches at up to 200MHz, regulating down to 0.6–1.0V over a 10μW–40mW output power range via use of DCM-PFM control. The converter occupies 1.5mm ² of silicon area (including a pair of 5nF flying capacitors and a 3nH inductor), and achieves a peak efficiency of 78%.