Transistor Downscaling toward Ultra-Low-Power, sub-100 mum2 and sub-Hz Oscillators

Abstract:
This paper analyses and discusses the feasibility of implementing sub-Hz range oscillators in ultra-low-power and ultra-miniaturised implants. The final aim is the Body Dust application, in which multiple freestanding smart cubes are wirelessly powered and freely to move in the human blood for bio-sensing purpose. That system requires an overall size smaller than 100 mum² and ultra-low power consumption. Two different CMOS technologies have been compared, analyzing the effect of transistor down-scaling in sub-Hz range oscillators. Four CMOSbased oscillators have been tested in both 0.18 mum and 28 nm technologies. The best result is the Schmitt Trigger-based timer implemented in FD-SOI 28 nm and combined with a ten stages frequency divider that oscillates at 122.5 mHz with a reduced area of 80 mum². The study demonstrate that the effect of transistor downscaling opens the possibility to reach a sub-Hz oscillator with both ultra-low-power and ultra-low-area consumption, so suitable for Body Dust application.