Temperature Stability Using Ring Oscillator Bi-Directional Counters

The internet of things (IoT) is envisaged to become an ultimate driver for the next growth phase of semiconductor industry. Lightweight electronic tagging technologies will avail themselves most in this ubiquitous computing revolution of advance connectivity of devices, systems and services. Unfortunately, the footprint and power budget have severely limited the strength of cryptographic algorithm implementable on radio frequency identification and other intelligent tags Ring oscillator (RO)-based physical unclonable function (PUF) is resilient against noise impacts, but its response is susceptible to temperature variations. This paper presents a low-power and small footprint hybrid RO PUF with a very high temperature stability, which makes it an ideal candidate for lightweight applications. The negative temperature coefficient of the low-power subthreshold operation of current starved inverters is exploited to mitigate the variations of differential RO frequencies with temperature. The new architecture uses conspicuously simplified circuitries to generate and compare a large number of pairs of RO frequencies.