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 approximate to 20 Hz. The oscillator was designed as a timer or clock generator for autonomous microsystem applications. The chip area of the oscillator is 18 mu m by 35 mu m 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.