11 1 University of Michigan 1 Phoenix: An Ultra-Low Power Processor for Cubic Millimeter Sensor System Motivations  Sensor application requires small form factor and long lifetime  Both limited by battery - A 1mm 2 zinc/silver battery with 100µAh/cm 2 can provides 177pW for 1 year lifetime  Either improve battery or power consumption  Minimize standby power (dominating portion of total power) via comprehensive standby strategy Bravo® pH Monitoring System VeriChip TM RFID Tag VeriChip

22 2 University of Michigan 2 Comprehensive standby strategy  Optimum technology selection  L=0.18µm, V dd =0.5V given performance, duty cycle and memory requirements  Unique power gating approach  SVT MOSFET with W=0.66µm L=0.5µm  Tradeoff performance with standby power  Ultra-low leakage sub-VTH SRAM design  7.1fW/bit custom SRAM cell  Adaptive power gating for dynamic standby power management  Power gating for peripherals  Robust ultra-low Vdd ROM design  full static NAND ROM design for robustness  Simple ISA with compression support  Narrow instruction for small IMEM footprint  Ultra-low power peripheral unit design  Slow watchdog timer  Low power temperature sensor

33 3 University of Michigan 3 Results  29.6pW for standby mode and 2.8pJ/cycle for active mode  100kHz at V dd =0.5V  1mm 2 in 0.18µm CMOS technology  2000 instructions for every 10min gives E active =5.6nJ, E standby =17.8nJ  Theoretically 15 year lifetime with a 1mm 2 thin film lithium battery Future works – designing more low power sub-modules including communication link, improve existing modules, variation compensation method, and system-level integration Thank you!