A PVT Tolerant True Random Number Generator Based on Oscillator Phase Under Sub-Harmonic Injection Locking

A digital true random number generator based on the oscillator phase generated by the second-order sub-harmonic injection locking phenomenon is proposed in this paper. Owing to the thermal jitter, the phase difference between a free-running (i.e., unsynchronized) oscillator and an injected external signal collapses to one of two stable solutions in a truly random manner. The injected external signal is generated from another oscillator operating at close to twice the frequency of the free-running oscillator. The random sequence extracted from the resulting stable solutions is bias- and correlation-free, nullifying the need for a bias compensation circuitry. The proposed design is demonstrated with extensive simulations to be robust under process, voltage, and temperature variations. The generated random patterns pass the National Institute of Standards and Technology test suite.