A 4.1 W/mm² hybrid inductive/capacitive converter for 2-140 mA-DVS load under inductor

This work presents a fully integrated hybrid inductive/capacitive converter maintaining high efficiency for a load range of 2 mA to 140 mA (70×) suitable for the dynamic voltage scaling (DVS) based loads. This high efficiency is achieved by using an inductive converter for higher loads (15-140 mA, 0.50-0.9 V) and a capacitive converter for lighter loads (2-5 mA, 0.40-0.55 V) with a 50 mV hysteresis margin. A digital state machine activates the appropriate converter based on the power efficiency and enables the converter hand-over. The functional feasibility of implementing digital circuits as representative loads under the inductor is shown thereby increasing the peak converter power density from 0.387 W/mm² to 4.1 W/mm² with only a minor hit on the efficiency. The maximum measured efficiency is achieved in inductive mode of operation and decreases from 76.4% to 71% when digital circuits are present under the inductor. The design was fabricated in IBM’s 32 nm SOI technology.