Flying and Decoupling Capacitance Optimization for Area-Constrained On-Chip Switched-Capacitor Voltage Regulators

Xiaoyang Mi1, Hesam Fathi Moghadam2 and Jae-sun Seo1
1School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, AZ, USA
2Oracle Labs, Redwood Shores, CA, USA


Switched-capacitor voltage regulators (SCVRs) are widely used in on-chip power management, due to high step-down efficiency and feasibility of integration. In this work, we present theoretical analysis and optimization methodology for flying and decoupling capacitance values for area-constrained on-chip SCVRs to achieve the highest system-level power efficiency. The proposed models for efficiency and droop voltage are validated with on-chip 2:1 SCVR implementations in both 65nm and 32nm CMOS, which show high model accuracy. The maximum and average error of the predicted optimal ratio between flying and decoupling capacitance are 5% and 1.7%, respectively.

Keywords: Switched-capacitor voltage converter, Integrated voltage regulator, Power conversion efficiency, Voltage droop, Capacitance optimization, Area-constrained power management.

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