Ring oscillator based random number generator utilizing wake-up time uncertainty

This paper presents a random number generation circuit utilizing ring oscillator´s wake-up time uncertainty. A ring oscillator goes into metastability state before starting to oscillate when its control voltage is increased from zero. The metastability causes the uncertainty of the wake-up time of the ring oscillator resulting in large jitter, which can be used for random number generation. We compared simple inverter and schmitt trigger type rings, number of stages of the rings, slow and fast control voltage change for the rings. The measurement results show that the slow control voltage change in a inverter type ring oscillator is effective for random number generation.