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Theses Doctoral

Integrated and Distributed Digital Low-Drop-Out Regulators with Event-Driven Controls and Side-Channel Attack Resistance

Kim, Sung Justin

A modern system-on-chip (SoC) integrates a range of analog, digital, and mixed-signal building blocks, each with a dedicated voltage domain to maximize energy efficiency. On-chip low-drop-out regulators (LDOs) are widely used to implement these voltage domains due to their advantages of high power density and the ease of integration to a complementary metal-oxide-semiconductor (CMOS) process. Recently, digital LDOs have gained large attention for their low input voltage support for emerging sub-mW SoCs, portability across designs, and process scalability. However, some of the major drawbacks of a conventional digital LDO design are (i) the trade-off between control loop latency and power dissipation which demands a large output capacitor, (ii) failure to address the performance degradations caused by the parasitics in a practical power grid, and (iii) insufficient power-supply-rejection-ratio (PSRR) and large ripple in the output voltage.

Chapters 2 through 4 of this thesis present my research on the design and circuit techniques for improving the aforementioned challenges in fully-integrated digital LDOs. The first work implements a hybrid event- and time-driven control in the digital LDO architecture to improve the response and settling time-related metrics over the existing designs. The second work presents a power delivery system consisting of 9 distributed event-driven digital LDOs for supporting a spatially large digital load. The proposed distributed LDO design achieves large improvements in the steady-state and non-steady-state performances compared to a single LDO design. In the third work, we prototype a digital LDO based on new current-source power-FETs to achieve a high PSRR and low output voltage ripple.

Lastly, on-chip voltage regulators have recently found usefulness in hardware security applications. An on-chip LDO can be used to improve the side-channel attack (SCA) resistance of a cryptographic core with design modifications to the classical LDO architecture. However, the existing designs incur non-negligible overheads in performance, power, and silicon area due to the conventional active-for-all-encryption-rounds architecture. In the last chapter, we propose a detection-driven activation technique to achieve a near-zero energy-delay-product (EDP) overhead in a SCA resilient digital LDO. In this architecture, the LDO can detect an attack attempt and enable SCA protection only if an attack is detected.


This item is currently under embargo. It will be available starting 2021-12-24.

More About This Work

Academic Units
Electrical Engineering
Thesis Advisors
Seok, Mingoo
Ph.D., Columbia University
Published Here
December 28, 2020