A Brief Overview of On-Chip Voltage Regulation in High-Performance and High-Density Integrated Circuits

With the increase of density and complexity of high performance integrated circuits and systems, including many-core chips and system-on-chip (SoC), it is becoming difficult to meet the power delivery and regulation requirements with off-chip regulators. The off-chip regulators become a less attractive choice because of the higher overheads and complexity imposed by the additional wires, pins, and pads. The increased I2R loss makes it challenging to maintain the integrity of different voltage domains under a lower supply voltage environment in the smaller technology nodes. Fully integrated on-chip voltage regulators have proven to be an effective solution to mitigate power delivery and integrity issues. Recently, there has been a surge of interest among the academic and industrial research communities to explore and design different types of on-chip voltage regulators. This survey presents a brief overview of the on-chip power delivery system and the classification and working principles of on-chip voltage regulators. The main focus of this review paper is to provide a comprehensive study of two of the most promising on-chip voltage regulators - (i) the low-drop-out (LDO) regulator and (ii) the switched-capacitor (SC) regulator. This article elaborates on the design specifications, optimization techniques, advantages, and limitations of LDO and SC type on-chip voltage regulators.