Fine-Grained Power-Gating Scheme of a Metal–Oxide–Semiconductor and Magnetic-Tunnel-Junction-Hybrid Bit-Serial Ternary Content-Addressable Memory

Abstract

A fine-grained power-gating scheme combining metal–oxide–semiconductor (MOS) transistors with magnetic-tunnel-junction (MTJ) devices, where storage data still remains even if the power supply is cut off, is proposed for an ultra low-power bit-serial ternary content-addressable memory (TCAM). Once a mismatched result is detected in a sequence of a bit-level equality-search operation, the power supply of all the cells in the word circuit is cut off, which greatly reduces the standby power dissipation in the word circuit. The standby power dissipation of the proposed TCAM in the standby mode is reduced to about 1.2% in comparison with that of a complementary MOS (CMOS)-only-based TCAM. Moreover, the power-delay product of the proposed TCAM is reduced to 15.5% in comparison with that of the corresponding CMOS-only-based TCAM.

Combination-Encoding Content-Addressable Memory With High Content Density

“…The application domain of the proposed CECAM fully covers other resistance-based NVMs with two-terminal switches, e.g., phase-change memory [14], [15] and magnetic tunnel junction [14], [17], in both active and passive arrays. Moreover, the CECAM concept is compatible with threeterminal NVMs, for instance, ferroelectric transistors [20] and NOR Flash memory.…”

“…Nevertheless, significant disadvantages are its low areal density due to the use of many transistors (≥8) to represent a single bit and high static power consumption due to the leakage current of SRAM [12]- [14]. As alternatives to the SRAM-based CAM, CAMs based on emerging non-volatile memories (NVMs) such as phase-change memory [14]- [16], magnetic tunnel junction [14], [17]- [19], ferroelectric memory [20], and resistance switch [21]- [25] have been proposed to date. Such NVM-based CAMs highlight their high data density and zero-static energy consumption due to the non-volatility.…”

Emerging Trends in Design and Applications of Memory-Based Computing and Content-Addressable Memories

“…2) CAM Bitcell: Fig. 5(b) shows a two-transistor-two-MTJ TCAM cell [45] where MTJ resistance is used for storing the bitcell content. The robustness of the MTJ TCAM design is sensitive to the tunneling magnetoresistance (TMR) between the high ðR high Þ and low resistances ðR low Þ of the MTJ.…”

Design of an energy-efficient 2T-2MTJ nonvolatile TCAM based on a parallel-serial-combined search scheme

“…The parallel-serial-combined search scheme achieves higher throughput (smaller search cycle count) than the bit-serial nonvolatile TCAM [3], although lower throughput than the bit-parallel one [6], while achieving power consumption between the bit-serial one and the bit-parallel one. In this section, we qualitatively analyze and evaluate the performance of the proposed nonvolatile TCAM with the parallel-serial-combined search scheme and finegrained power-gating scheme.…”

“…To overcome these problems, we have proposed magnetic tunnel junction (MTJ)-based word-parallel/bit-serial nonvolatile TCAMs with a twotransistor/two-MTJ-device (2T-2MTJ) cell structure and a bit-level finegrained power gating scheme [2,3,4,5]. The bit-level search in a word circuit achieved ultra-low cell activity with fine-grained power gating resulting in ultra-low active and standby power consumption, while it caused a decrease in search speed.…”