A Pulse-Frequency Modulation (PFM)-based SoC-compatible buck converter is designed in scaled-CMOS technology. Taking an input supply of 2.7V-4.2V, it delivers a 0.55V output. It supports a load-current of 0.5mA to 10mA with > 80% efficiency throughout, and 84.7% peak-efficiency on silicon. To achieve this, it employs a low-power Bandgap reference, push-pull voltage-buffers with adaptive-biasing, duty-cycled sensors, and a failsafe asynchronous loop. Device stress is managed for each sub-block viz., a stacked power stage is used. It targets Standby-mode (0.5mA to 10mA) of operation for Internet-of-Things (IoT) applications and is to be integrated with Sleep-mode (10uA-0.5mA) and Active-mode (10mA-100mA) counterparts.