TY - GEN
T1 - Fully-integrated switched-capacitor voltage regulator with on-chip current-sensing and workload optimization in 32nm SOI CMOS
AU - Mi, Xiaoyang
AU - Mandal, Debashis
AU - Sathe, Visvesh
AU - Bakkologlu, Bertan
AU - Seo, Jae-sun
PY - 2015/9/21
Y1 - 2015/9/21
N2 - Efficient, stable, and fast power delivery against fluctuating workloads have become a critical concern for applications from battery-powered devices to high-performance servers. With high density on-chip capacitors, fully-integrated switched-capacitor (SC) voltage converters provide high efficiency down-conversion from a battery or off-chip voltage regulation modules. However, maintaining such efficiency with minimal supply noise across a wide range of fluctuating load currents remains challenging. In this paper, we propose an on-chip current sensing technique to dynamically modulate both switching frequency and switch widths of SC voltage converters, enhancing fast transient response and higher efficiency across a wide range of load currents. In conjunction with SC converters, we employ a low-dropout regulator (LDO) driven by a push-pull operational transconductance amplifier (OTA), whose current is mirrored and sensed with minimal power and efficiency overhead. The sensed load current directly controls the frequency and width of SC converters through a voltage-controlled oscillator (VCO) and a time-to-digital converter, respectively. In 32nm SOI CMOS, the proposed voltage regulator maintains 77-82% efficiency at 0.95V output voltage with less than 20mV steady-state ripple across 10X load current range of 100mA-1A and 33mV droop voltage for a 80mA/ns load transition, while providing a projected current density of 6W/mm2.
AB - Efficient, stable, and fast power delivery against fluctuating workloads have become a critical concern for applications from battery-powered devices to high-performance servers. With high density on-chip capacitors, fully-integrated switched-capacitor (SC) voltage converters provide high efficiency down-conversion from a battery or off-chip voltage regulation modules. However, maintaining such efficiency with minimal supply noise across a wide range of fluctuating load currents remains challenging. In this paper, we propose an on-chip current sensing technique to dynamically modulate both switching frequency and switch widths of SC voltage converters, enhancing fast transient response and higher efficiency across a wide range of load currents. In conjunction with SC converters, we employ a low-dropout regulator (LDO) driven by a push-pull operational transconductance amplifier (OTA), whose current is mirrored and sensed with minimal power and efficiency overhead. The sensed load current directly controls the frequency and width of SC converters through a voltage-controlled oscillator (VCO) and a time-to-digital converter, respectively. In 32nm SOI CMOS, the proposed voltage regulator maintains 77-82% efficiency at 0.95V output voltage with less than 20mV steady-state ripple across 10X load current range of 100mA-1A and 33mV droop voltage for a 80mA/ns load transition, while providing a projected current density of 6W/mm2.
KW - low-dropout regulator
KW - on-chip current sensing
KW - switched-capacitor voltage converter
KW - voltage-controlled oscillator
UR - http://www.scopus.com/inward/record.url?scp=84958530540&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84958530540&partnerID=8YFLogxK
U2 - 10.1109/ISLPED.2015.7273504
DO - 10.1109/ISLPED.2015.7273504
M3 - Conference contribution
AN - SCOPUS:84958530540
T3 - Proceedings of the International Symposium on Low Power Electronics and Design
SP - 140
EP - 145
BT - Proceedings of the International Symposium on Low Power Electronics and Design, ISLPED 2015
PB - Institute of Electrical and Electronics Engineers Inc.
T2 - 20th IEEE/ACM International Symposium on Low Power Electronics and Design, ISLPED 2015
Y2 - 22 July 2015 through 24 July 2015
ER -