A RISC-V Vector Processor With Simultaneous-Switching Switched-Capacitor DC–DC Converters in 28 nm FDSOIAuthors: Brian Zimmer, Yunsup Lee, Alberto Puggelli, Jaehwa Kwak, Ruzica Jevtic, Ben Keller, Stevo Bailey, Milovan Blagojevic, Pi-Feng Chiu, Hanh-Phuc Le, Po-Hung Chen, Nick Sutardja, Rimas Avizienis, Andrew Waterman, Brian Richards, Philippe Flatresse, Elad Alon, Krste Asanovic, Bora Nikolic
Date: April 2016
Conference: Journal of Solid-State Circuits (JSSC)
This work demonstrates a RISC-V vector microprocessor implemented in 28 nm FDSOI with fully integrated simultaneous-switching switched-capacitor DC–DC (SC DC–DC) converters and adaptive clocking that generates four on-chip voltages between 0.45 and 1 V using only 1.0 V core and 1.8 V IO voltage inputs. The converters achieve high efficiency at the system level by switching simultaneously to avoid charge-sharing losses and by using an adaptive clock to maximize performance for the resulting voltage ripple. Details about the implementation of the DC–DC switches, DC–DC controller, and adaptive clock are provided, and the sources of conversion loss are analyzed based on measured results. This system pushes the capabilities of dynamic voltage scaling by enabling fast transitions (20 ns), simple packaging (no off-chip passives), low area overhead (16%), high conversion efficiency (80%–86%), and high energy efficiency (26.2 DP GFLOPS/W) for mobile devices.