Precharge-free Content-addressable Memory Research Articles

Low power CMOS based Self Controlled Precharge Free Content Addressable Memory with Minimum area for Image Processing Devices

Image processing devices plays a vital role in several applications like medical, security, biometric etc. The devices ranges from portable size to larger machines with and without Human Computer Interface possibilities. As the image processing and human computer interface system application requires higher memory requirements, the power and area should be small. Searching of data is a high priority work in image classification. To perform high speed search through hardware Content Addressable Memory is used. But the circuit suffers from higher power consumption, precharging issues and low performance. For longer word length the elimination of precharge is needed. So for high speed applications self-controlled precharge-free CAM (SCPF-CAM) is suitable. A 4T hybrid self controlled pre charge free Content Addressable Memory is proposed in this paper using CMOS 32nm technology. The observation shows that the circuit works at high speed, minimizes the search time and has high performance operation. When compared to the conventional SCPF-CAM, 8T CAM the proposed design reduces the number of transistors. The reduction in area is about approximately 20% and can be used in low power and low energy applications. In Synopsis HSPICE Predictive technology models were used for the implementation in 32nm CMOS technology. The work will be extended in future using FinFET technology where the leakage current can be minimized.

Energy-Efficient Precharge-Free Ternary Content Addressable Memory (TCAM) for High Search Rate Applications

Hardware search engines (HSEs) have been drawing significant attention in replacing software search algorithms in order to speed up location access and data association in modern systems. Content addressable memory (CAM) is one of the promising HSEs due to its parallel search accessibility. However, it is subjected to considerable dissipation which becomes severe while accessing many components including cells and associated matchlines (MLs) during every search. Ternary CAM (TCAM) based routing tables, especially employed in network systems for packet classification, has put a challenge to design energy-efficient architectures with high-performance and reliable look-up operation. Precharge-free CAM schemes are preferred solutions over precharge types to accomplish high-speed as well as low-power goals of associative memory design. In order to overcome the drawbacks of precharge based designs and also to improve performance during the search, we introduce a precharge-free ternary content addressable memory (PF-TCAM). The proposed searching approach enhances the rate of search by reducing half of the ML evaluation time as it eliminates precharge phase prior to every search by performing search in HALF clock cycle. A $32\times 16$ -bit proposed macro is designed using 45-nm CMOS technology and post-layout simulations at 1 V supply shows 56% and 63% energy efficiency improvements compared to conventional TCAM and compact TCAM respectively over 25 different search keys despite increasing evaluation speed by 50% with an area overhead of 1 transistor/cell over compact TCAM.

Hybrid self-controlled precharge-free CAM design for low power and high performance

Content-addressable memory (CAM) is a prominent hardware for high-speed lookup search, but consumes larger power. Traditional NOR and NAND match-line (ML) architectures suffer from a short circuit current path sharing and charge sharing respectively during precharge. The recently proposed precharge-free CAM suffers from high search delay and the subsequently proposed self-controlled precharge-free CAM suffers from high power consumption. This paper presents a hybrid self-controlled precharge-free (HSCPF) CAM architecture, which uses a novel charge control circuitry to reduce search delay as well as power consumption. The proposed and existing CAM ML architectures were developed using CMOS 45nm technology node with a supply voltage of 1 V. Simulation results show that the proposed HSCPF CAM-type ML design reduces power consumption and search delay effectively when compared to recent precharge-free CAM-type ML architectural designs.

Self-Controlled High-Performance Precharge-Free Content-Addressable Memory

Content-addressable memory (CAM) is a hardware search-engine used for parallel lookup that assures high-speed match but at the cost of higher power consumption. Both low power NAND-type and high-speed NOR-type match-line (ML) schemes suffer from requirement of the precharge prior to the search. Recently, a precharge-free ML structure has been proposed but with inadequate search performance. In this brief, a self-controlled precharge-free CAM (SCPF-CAM) structure is proposed for high-speed applications. The proposed architecture is useful in applications where search time is very crucial to design larger word lengths. The proposed $128 \times 32$ -bit SCPF-CAM structure has been implemented using predictive 45-nm CMOS process and simulated in SPECTRE at the supply voltage of 1 V. The ML delay using the proposed SCPF-CAM architecture has been reduced by 88% and 73% compared to the precharge-free and traditional NAND-type ML structure.

Precharge-Free, Low-Power Content-Addressable Memory

Content-addressable memory (CAM) is the hardware for parallel lookup/search. The parallel search scheme promises a high-speed search operation but at the cost of high power consumption. Parallel NOR- and NAND-type matchline (ML) CAMs are suitable for high-search-speed and low-power-consumption applications, respectively. The NOR-type ML CAM requires high power, and therefore, the reduction of its power consumption is the subject of many reported designs. Here, we report and explore the short-circuit (SC) current during the precharge phase of the NOR-type ML. Also proposed here is a novel precharge-free CAM. The proposed CAM is free of the drawbacks of the charge sharing in the NAND and the SC current in the NOR-type CAM. Postlayout simulations performed with a 45-nm technology node revealed a significant reduction in the energy metric: 93% and 77% lesser than NOR- and NAND-type CAMs, respectively. The Monte Carlo simulation for 500 runs was performed to ensure the robustness of the proposed precharge-free CAM.