Ultra-low Power Access Strategy for Process-Voltage-Temperature Aware STT-MRAM

Abstract

With the development of circuit integration, low power consumption design has become the design challenge of on-chip memory. This work focuses on ultra-low power access strategy for STT-MRAM. A high margin voltage sensing amplifier (VSA) is implemented based on the bit-line (BL) parasitic capacitance, whereas a pulse-detect write self-termination is included for MRAM writing. Simulation is performed based on 28-nm CMOS and 40-nm CD magnetic tunnel junction (MTJ). Monte Carlo simulation show that the proposed sensing circuit achieves a reading yield of over 98% as well as 38% energy saving compared to previous work. Meanwhile, the self-termination scheme achieves an energy saving for more than 80%. These MRAM access strategies is well-adapted to process-voltage-temperature (PVT) variations including Tunnel Magneto Resistance (TMR) (20%-200%), temperature (0℃-120℃) and supply voltage (0.6V-1.8V).