Analog Content-Addressable Memory Using Floating Gate Devices

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Solution Overview

Problem

Conventional content-addressable memories (CAMs) are limited in their ability to efficiently store and search analog data, as they primarily utilize binary or ternary states, which restricts their functionality in applications requiring high-speed pattern matching and search operations.

Innovation Solution

An analog content-address memory (CAM) is developed using floating gate devices, where a combination of N-type and P-type channel floating gate devices are connected in series or parallel to set a match range, allowing for the storage and matching of analog data by determining if an input signal falls within a predetermined voltage level, enabling efficient matching and mismatch results.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If binary or ternary states are used for storage in conventional CAM, then the device complexity is reduced and ease of manufacture is improved, but the functionality for analog data storage and search is limited

Engineering Contradiction:

Improveanalog data storage capabilityVSAvoidmemory cell structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent transitions from binary/ternary discrete states to continuous analog voltage states for data storage. Floating gate devices are programmed to store specific threshold voltages that represent analog values, enabling the CAM to store and search analog data with matched precision rather than discrete categories.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces traditional digital logic-based comparison mechanisms with analog voltage-based matching using floating gate devices. The memory cells use voltage threshold comparisons rather than binary state comparisons, substituting digital logic operations with analog electrical field interactions.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If conventional binary CAM is used, then the manufacturing process is simplified, but the speed and efficiency of pattern matching operations are insufficient for high-performance applications

Engineering Contradiction:

Improvesearch operation speedVSAvoidfabrication process

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent pre-programs floating gate devices with specific threshold voltages during manufacturing to encode analog data values. This preliminary programming establishes the matching criteria in advance, allowing the CAM to perform high-speed analog pattern matching without requiring complex real-time computation or multiple processing stages.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If floating gate devices with series connection are used, then the match range precision is improved, but the device occupies larger area

Engineering Contradiction:

Improvematch range accuracyVSAvoidmemory cell area

Core Design Contradiction:

Measurement precisionVSArea of moving object

Solution Approach 1:

The patent divides the memory cell into two separate floating gate devices connected in series, each responsible for storing one bit of the analog value. This segmentation allows independent programming and precise control of threshold voltages while maintaining a compact series connection that reduces overall cell area compared to parallel configurations.

Inventive Principle:

Principle #1Segmentation

4Adaptability or versatility

If floating gate devices are programmed to store analog data, then the functionality for high-speed search is enhanced, but the programming complexity increases

Engineering Contradiction:

Improveanalog pattern matching capabilityVSAvoidprogramming process

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent employs self-aligned floating gate structures where the programming process automatically establishes the threshold voltage based on the applied programming pulses. The device structure itself facilitates the programming operation, reducing the need for complex external control circuitry or multiple programming steps.

Inventive Principle:

Principle #25Self-service

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The analog CAM effectively stores and identifies matching analog data by adjusting the match range through programming, enhancing the memory's ability to perform high-speed searches and pattern matching beyond binary limitations.

Implementation Method 1

floating gate devices are used for storing analog data

Methodology Applied

Scientific EffectCharge trapping: Electrical Accumulator

Implementation Method 2

the sense amplifier outputs a match result

Methodology Applied

Scientific EffectVoltage detection: Electric Field

Data Source

PatentUS11657876B2Analog content-address memory and operation method thereof

Publication Date: 2023.05.23 MACRONIX INTERNATIONAL CO LTD

AI summary

An analog CAM and an operation method thereof are provided. The analog CAM includes a matching line, an analog CAM cell and a sense amplifier. Each of the at least one analog CAM includes a first floating gate device having a N type channel and a second floating gate device having a P type channel. A match range is set through programming the first floating gate device and the second floating gate device. The sense amplifier is connected to the matching line. If an inputting signal is within the match range, a voltage of the matching line is pulled down to be equal to or lower than a predetermined level. The sense amplifier outputs a match result if the voltage of the matching line is pulled down to a predetermined level.