A Calibration-Free In-Memory True Random Number Generator Using Voltage-Controlled MRAM

In this paper, we propose an in-memory True Random Number Generator (TRNG) using Voltage-Controlled MRAM that doesn't require calibration of the writing pulse's width and amplitude. Previous solution using Spin Transfer Torque (STT) MRAM requires calibration for every MTJ, thus making the multi-row random number generation inside the memory impossible. We also propose a 100% relative throughput digital bias correction circuit that doesn't degrade bit rate. The VC- MTJs are fabricated in CMOS BEOL compatible process with an 80 nm diameter and high TMR ratio of 160%. MRAM array circuits and bias correction circuits are fabricated in 65 nm CMOS technology and wire-bonded with the VC-MTJ devices. Multiple VC-MTJs are tested and shown to pass all NIST randomness tests.