A Low Power Reconfigurable Memory Architecture for Complementary Resistive Switches

Abstract

Memristive crossbar array suffers from severe sneak currents that incur reliability issues and extra energy waste. Complementary resistive switches (CRSs) provide a new concept to address the sneak-current problem. But the destructive read of CRS results in an additional recovery write operation, which strongly restricts its further promotion. Exploiting the dual CRS/memristor mode of CRS devices, we propose Aliens , a novel reconfigurable architecture that introduces one alien cell (memristor mode) for each bitline in the crossbar. Aliens draws advantages from both modes: restrained sneak currents of the CRS mode and nondestructive read of the memristor mode. The simple and regular cell mode organization one bitline one memristor (OBOM) of Aliens enables an energy-saving read method. Further, by exploiting memory access locality, an effective mode switching strategy called Lazy-Switch is proposed to delay and merge the recovery write operations of the CRS mode. Moreover, an 1TnR crossbar structure is adopted to enable larger crossbar arrays as well as a higher ratio of memristor mode cells without going against the OBOM rule. The effects of the memristor mode cell ratio on the energy consumption, endurance, and access performance are studied. Also, we show the bank architecture of Aliens and analyze how to extend our designs to 3-D arrays. Due to fewer recovery write operations and negligible sneak currents, Aliens achieves improvements in energy, overall endurance, and access performance. The experimental results show that our design offers average energy savings of $19.1\times $ compared with memristor-only memory, a memory lifetime $10.7\times $ longer than CRS-only memory, and a competitive performance compared with memristor-only memory.