Power Management and SRAM for Energy-Autonomous and Low-Power Systems

Power Management;DC-DC Conversion;SRAM;Energy Harvesting;Photovoltaic Power Systems;Cubic-millimeter Microsystems;Electrical Engineering;Engineering;Electrical Engineering

Chen, Gregory K.Wentzloff, David D. ;

University of Michigan

关键词: Power Management;    DC-DC Conversion;    SRAM;    Energy Harvesting;    Photovoltaic Power Systems;    Cubic-millimeter Microsystems;    Electrical Engineering;    Engineering;    Electrical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/86387/grgkchen_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

We demonstrate the two first-known, complete, self-powered millimeter-scale computer systems.These microsystems achieve zero-net-energy operation using solar energy harvesting andultra-low-power circuits. A medical implant for monitoring intraocular pressure (IOP) is presentedas part of a treatment for glaucoma. The 1.5mm3 IOP monitor is easily implantable because of itssmall size and measures IOP with 0.5mmHg accuracy. It wirelessly transmits data to an externalwand while consuming 4.7nJ/bit. This provides rapid feedback about treatment efficacies to decreasephysician response time and potentially prevent unnecessary vision loss. A nearly-perpetualtemperature sensor is presented that processes data using a 2.1μW near-threshold ARM°R Cortex-M3TM μP that provides a widely-used and trusted programming platform.Energy harvesting and power management techniques for these two microsystems enable energy-autonomousoperation. The IOP monitor harvests 80nW of solar power while consuming only5.3nW, extending lifetime indefinitely. This allows the device to provide medical information forextended periods of time, giving doctors time to converge upon the best glaucoma treatment. Thetemperature sensor uses on-demand power delivery to improve low-load dc-dc voltage conversionefficiency by 4.75x. It also performs linear regulation to deliver power with low noise, improvedload regulation, and tight line regulation.Low-power high-throughput SRAM techniques help millimeter-scale microsystems meet stringentpower budgets. VDD scaling in memory decreases energy per access, but also decreases stabilitymargins. These margins can be improved using sizing, VTH selection, and assist circuits,as well as new bitcell designs. Adaptive Crosshairs modulation of SRAM power supplies fixes70% of parametric failures. Half-differential SRAM design improves stability, reducing VMIN by72mV.The circuit techniques for energy autonomy presented in this dissertation enable millimeter-scalemicrosystems for medical implants, such as blood pressure and glucose sensors, as well asnon-medical applications, such as supply chain and infrastructure monitoring. These pervasivesensors represent the continuation of Bell’s Law, which accurately traces the evolution of computersas they become smaller, more numerous, and more powerful. The development ofmillimeter-scale massively-deployed ubiquitous computers ensures the continued expansion andprofitability of the semiconductor industry. NanoWatt circuit techniques will allow us to meet thisnext frontier in IC design.