Improved On-Chip Inductor Design for Fully Integrated Voltage Regulators

This article presents a simple procedure to optimally design an on-chip spiral inductor, which is normally a major challenge in fully integrated voltage regulator (FIVR) applications. To develop the design method, a simplified model is proposed and evaluated that describes the inductance and resistance values of an on-chip spiral inductor according to its geometric properties. Maximizing the quality factor -based on the inductor total resistance- and minimizing the power loss -based on the inductor total resistance and its current waveform- in the minimum possible chip area are two different goals that are achieved. Two design methods are presented to provide optimal geometric specifications of the on-chip inductor. The design methods are simple and do not require complex simulation iterations. In addition, 3-D electromagnetic simulation is used to extract the characteristics of the designed on-chip spiral inductors to perform comparisons and the verification of the effectiveness of the proposed design methods.