Reading spin-torque memory with spin-torque sensors

Spin-Transfer-Torque Magnetic Random Access Memory (STT-MRAM) is a promising candidate for future on-chip memory, owing to its high-density, zero-leakage and energy efficiency. In a conventional STT-MRAM cache write operations consume larger energy as compared to read, due to relatively large write-current requirement. In recent years novel spin-torque based write schemes have been proposed for MRAM that can bring large reduction in write energy, such that the read-energy now becomes dominant. Conventional read schemes based on CMOS sense amplifiers may not offer commensurate reduction in read energy, owing to their poor scalability and limited speed. We propose a spin-torque based sensing technique for MRAM that employs nano-scale spin-torque switches for low-voltage, low-current read-operations in STT-MRAM. Such a sensing-scheme can achieve improved-scalability, simplified-design for read-peripherals, high-speed read-operations and 90% lower read-energy. As a result more than ~80% reduction in overall energy can be obtained for STT-MRAM based caches.