This paper reports a high-frequency DC-DC boost converter capable of sustaining up to 4× the rated process voltage using high-voltage devices fabricated in standard 0.13 μm 1.2 V CMOS without additional masking steps. Integrated Schottky Barrier Diodes (SBD) and high-voltage stacked composite NMOS switches enable processing of large voltages in a 100 MHz digitally assisted four-phase switched inductor (SI) boost converter architecture. A high-frequency digital delay-locked loop (DDLL) is employed to automatically stagger and synchronize each phase to a primary current-mode pulsed-width modulator (PWM) controller, thus eliminating the need for multiple current sensing circuits. The converter operates in discontinuous conduction mode (DCM) and utilizes integrated Schottky diode output rectifier stages to eliminate dead-time controllers and power hungry high side drivers. The converter operates at 100 MHz with four external 22 nH inductors and achieves an output conversion range of 3 V to 5 V from a 1.2 V input supply. It can deliver 240 mW at 3 V and 200 mW at 5 V with an efficiency of 60%, and ~ 180 mW at 3 V with peak efficiency of 64%.