A 10T-4MTJ Nonvolatile Ternary CAM Cell for Reliable Search Operation and a Compact Area

Abstract

Ternary content addressable memory (TCAM) is widely used in high-speed searching applications. Recently, zero standby power has been in high demand for battery-powered devices such as mobile phones, Internet of Things, and wearable devices. Thus, several nonvolatile TCAM (NV-TCAM) cells have been researched to realize zero standby power. However, they suffer from low reliability in search operation. We propose a 10T-4MTJ NV-TCAM cell that significantly improves the reliability of search operation utilizing the differential sensing and positive feedback of cross-coupled PMOSs. The advantages of the proposed cell are verified by HSPICE Monte Carlo simulations using industry-compatible 45-nm model parameters. With a cell area of 2.78 $\mu\text{m}^{2}$ (1.12 times smaller than a SRAM-based TCAM cell) and a search delay of 1 ns, the proposed cell satisfies a target search pass yield of $6\sigma$ (98.24% yield for an 18-Mb TCAM macro), whereas the previous cells achieved only 3.3 and $3.6\sigma$ .