A self-regulated 588 MHz buck regulator with on-chip passives and circuit stuffing in 65nm

A fully-integrated buck regulator with on-chip passives in 65nm standard CMOS technology is presented. The proposed regulator switches at 588MHz and uses a 20nH on-chip inductor and a 300pF on-chip output capacitor. It operates from 1.8V input and produces an output in the range between 0.8V to 1.2V with maximum load current of 30mA. In order to reduce the large silicon area overhead of the on-chip inductor, the proposed design employs circuit stuffing where the entire regulator´s circuitry is implemented directly underneath the inductor. This includes the input and output capacitance, power train, and control circuits. Thus, the total area of the regulator becomes essentially the area of the on-chip inductor itself, which cuts the regulator´s footprint by 50%. Moreover, the proposed regulator employs a self-regulation loop that improves its overall efficiency and ensures the reliability of its low-voltage power transistors while operating from a 1.8V input. The regulator occupies 0.12mm² with a peak efficiency of 60%, and achieves up to 13.7% better efficiency than a corresponding LDO. It achieves fast settling time of 240ns for a 200mV output voltage step, and as short as 40ns for a 20mA load current step.