A Fully Integrated Li-Ion-Compatible Hybrid Four-Level DC–DC Converter in 28-nm FDSOI

This paper presents a Li-ion-compatible fully integrated hybrid dc–dc converter implemented in 28-nm FDSOI. A modified four-level converter is proposed to achieve high efficiency while operating from the 2.8–4.2-V Li-ion battery range by using stacked 1.5-V transistors. In this paper, the proposed driver architecture exploits the internal nodes of the power stage as power/GND rails for drivers, eliminating the need for dedicated power rails, level shifters, or stacked drivers. The proposed converter operates in the discontinuous conduction mode (DCM) and regulates the output with constant ON-time pulse-frequency modulation (PFM), to achieve high efficiency across low load range suitable for wearable/Internet of Things (IoT) applications. The fabricated chip regulates a 0.6–1.2-V output from a 2.8–4.2-V input voltage over an output power range from $10~\mu \textrm {W}$ to 40 mW with 78% peak efficiency, and switching frequency up to 200 MHz. The converter occupies $1.5~\textrm {mm}^{2}$ of on-die area including a pair of 5-nF flying capacitors and a 3-nH inductor.