Ultra low-power, -area and -frequency CMOS thyristor based oscillator for autonomous microsystems

In this paper we present a minimal sized CMOS thyristor based oscillator, which is able to provide a clock signal of ≈\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\approx$$\end{document}20 Hz. The oscillator was designed as a timer or clock generator for autonomous microsystem applications. The chip area of the oscillator is 18 µm by 35 µm and it is able to run for more than 10 min when supplied from a 10 nF capacitor. The oscillator’s time constant is determined by MOS transistor leakage currents and MOS capacitances. It could be shown that there is no need for large on chip resistors and capacitors. A chip was fabricated in a standard 180 nm CMOS technology and evaluated. The measured power consumption at 200 mV and 1.8 V supply voltage is 3 and 232 pW, respectively. We also investigated the ability of the oscillator to operate without a package by measuring the influence of incident light to current consumption and oscillation frequency. The possibility to tune the frequency of thyristor based oscillators has been investigated with a second test chip.