A Monolithic All-1.8 V-Thin-Gate-NMOS KY-Boost Converter With Reused Flying-Capacitor Bootstrap Gate Driver Achieving 94.42% Peak Efficiency

This article presents a monolithic KY-boost converter for wearable display systems. Traditional boost converter for this application suffers from large chip area and bulky output filter. This article proposes a monolithic KY-boost converter using all-1.8V-thin-gate-NMOS switches to reduce power loss and silicon area. Without an extra off-chip bootstrap capacitor, this proposed converter reuses the flying capacitor as the bootstrap capacitor for one of the high-side switches. Meanwhile, an internal charge-pump-based gate driver is introduced to drive another high-side switch. Furthermore, the soft-charging startup circuit and peak-current mode control for this KY converter are realized. The converter integrated circuit (IC) is realized in a 180 nm CMOS process with an input voltage of 1.5–1.8 V, an output of 2–2.7 V, a maximum power efficiency of 94.42%, and a 0.695 W/mm
²
power density. Thanks to the all-thin-gate-NMOS architecture, the proposed converter reduces more than 75% of silicon area with the same IC pin count compared to the conventional boost converter and P-P-NMOS thick-gate KY-boost converter.