33-200Mbps, 3pJ/bit True Random Number Generator Based on CT Delta-Sigma Modulator

This work presents a true random number generator (TRNG) that uses noise and jitter in a continuous-time, deltasigma modulator (CTDSM) as entropy source. A multi-bit non-return-to-zero (NRZ) feedback digital-to-analog converter (DAC) ensures that input swing seen by the front-end integrators is small and dominated by CTDSM noise and jitter, thus allowing the proposed circuit to simultaneously operate as both CTDSM and TRNG which is a key differentiation of this work compared to state-of-the-art TRNGs. Voltage controlled ring oscillators are used to implement integrators in the proposed CTDSM. Fabricated in 65nm CMOS, the TRNG has an energy efficiency of 3pJ/bit at throughput of 33Mbps and 3.5pJ/bit at 200Mbps, and passes all NIST tests with a minimum pass rate> 0.96. The measured minimum entropy of the TRNG bits is > 0.9995 across multiple chips and voltage/temperature corners without any calibration.