An ultra-low power wake-Up timer compatible with n-FET based flexible technologies

Abstract

Flexible integrated circuits (FlexICs) have drawn increasing attention, particularly in remote sensors and wearables operating in a limited power budget. Here, we present an ultra-low power timer designed to wake-up an external circuit periodically, from a deep-sleep state into an active state, thereby largely reducing the system power consumption. We achieved this with a circuit topology that exploits the transistor’s leakage current to generate a low frequency wake-up signal. This topology is compatible with IC technologies where only n-type transistors are available. The design was implemented with the sustainable FlexIC process of PragmatIC, that is based on Indium Gallium Zinc Oxide (IGZO) thin-film transistors. Our timer generates mean wake-up frequency of 0.24 ± 0.15 Hz, with a mean power consumption of 26.7 ± 14.1 nW. In this paper, we provide details of the Wake-Up timer’s design and performance at different supply voltages, under temperature variations and different light conditions.