Six-Transistor CAM Cell Reducing Transistor Count

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Solution Overview

Problem

Existing content-addressable memory (CAM) cells, such as the 10-T NOR-type and 9-T NAND-type cells, have a high number of transistors, leading to increased cost and power consumption.

Innovation Solution

A six-transistor (6-T) CAM cell design comprising a first and second switch, and a storage unit with cross-coupled inverters, where the switches control electrical connections based on complementary search signals, reducing the number of transistors and simplifying the circuit structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional 10-T or 9-T CAM cell designs are used, then search functionality is achieved, but transistor count increases leading to higher cost and power consumption

Engineering Contradiction:

Improvesearch functionalityVSAvoidtransistor count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts and removes redundant transistors from the traditional CAM cell structure. By carefully analyzing the search functionality requirements, the design eliminates unnecessary transistors while retaining the core match detection capability, achieving a reduced transistor count that lowers complexity and power consumption

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent merges multiple transistor functions into fewer devices. The search functionality is achieved by combining the roles of traditional separate transistors into a more integrated structure where transistors serve multiple purposes simultaneously, reducing the overall transistor count while maintaining functionality

Inventive Principle:

Principle #5Merging (Combining)

2Reliability

If traditional 10-T or 9-T CAM cell designs are used, then search functionality is achieved, but power consumption increases due to more transistors

Engineering Contradiction:

Improvesearch functionalityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by stationary object

Solution Approach 1:

The patent removes redundant transistors that contribute to power consumption without compromising search functionality. By extracting only the essential components needed for match detection, the design reduces the number of active devices that consume power during search operations

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent changes the operational parameters of the CAM cell by using complementary search signals (SL and SLB) that are inverses of each other. This allows the circuit to achieve the same search functionality with fewer transistors, thereby reducing static and dynamic power consumption associated with maintaining and switching additional devices

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS10885981B2Content-addressable memory having six-transistor content-addressable memory cells

Publication Date: 2021.01.05 UNITED MICROELECTRONICS CORP

AI summary

A cell of a content-addressable memory (CAM) has a first switch, a second switch and a storage unit. A first end of the first switch and a first end of the second switch are coupled to a matchline. The first switch is controlled by a first search signal, and the second switch is controlled by a second search signal. The second search signal is complementary to the first search signal. The storage unit has a first inverter and a second inverter. The first inverter has a first latch node coupled to a second end of the first switch. The second inverter is cross-coupled to the first inverter and has a second latch node coupled to a second end of the second switch.