Match Line Equalizer Circuit for TCAM Power Reduction

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Solution Overview

Problem

Content addressable memory (CAM) devices face challenges with high power consumption and peak current due to large peak currents when charging and discharging match lines, leading to electromagnetic interference, power-supply noise, and increased costs, which hinder the expansion of CAM array capacity.

Innovation Solution

Incorporating a match line equalizer circuit with switches connected between match lines and a power source or ground, allowing the controller to adjust match line potentials to half the power source voltage, reducing power consumption and peak current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If the capacity of the CAM array is increased, then the data search capability is improved, but the peak current increases causing electromagnetic interference and power-supply noise

Engineering Contradiction:
ImproveCAM array capacityVSAvoidelectromagnetic interference and power-supply noise
Core Design Contradiction:
Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

The patent applies equipotentiality by equalizing the potentials of complementary match lines (MLp and MLn) to the same voltage level (VDD/2) before comparison operations. This is achieved through dedicated equalizer circuits that adjust the potential of each match line to match a reference potential. By maintaining equal potentials before operations and restoring equal potentials after operations, the invention eliminates potential differences that would otherwise cause large current flows, thereby reducing electromagnetic interference and power-supply noise while enabling increased CAM array capacity.

Inventive Principle:
Principle #12Equipotentiality

2Quantity of substance

If the capacity of the CAM array is increased, then the data search capability is improved, but the voltage drop increases

Engineering Contradiction:
ImproveCAM array capacityVSAvoidvoltage drop
Core Design Contradiction:
Quantity of substanceVSStress or pressure

Solution Approach 1:

The patent applies equipotentiality by equalizing the potentials of complementary match lines (MLp and MLn) to the same voltage level (VDD/2) before comparison operations. This is achieved through dedicated equalizer circuits that adjust the potential of each match line to match a reference potential. By maintaining equal potentials before operations and restoring equal potentials after operations, the invention eliminates potential differences that would otherwise cause large current flows, thereby reducing electromagnetic interference and power-supply noise while enabling increased CAM array capacity.

Inventive Principle:
Principle #12Equipotentiality

3Quantity of substance

If the capacity of the CAM array is increased, then the data search capability is improved, but the total current consumption increases

Engineering Contradiction:
ImproveCAM array capacityVSAvoidtotal current consumption
Core Design Contradiction:
Quantity of substanceVSUse of energy by moving object

Solution Approach 1:

The patent applies equipotentiality by equalizing the potentials of complementary match lines (MLp and MLn) to the same voltage level (VDD/2) before comparison operations. This is achieved through dedicated equalizer circuits that adjust the potential of each match line to match a reference potential. By maintaining equal potentials before operations and restoring equal potentials after operations, the invention eliminates potential differences that would otherwise cause large current flows, thereby reducing electromagnetic interference and power-supply noise while enabling increased CAM array capacity.

Inventive Principle:
Principle #12Equipotentiality

Solution Approach 2:

The patent applies parameter changes by dynamically adjusting the potential of match lines to VDD/2 before comparison operations and restoring them to their initial states after operations. This controlled parameter change eliminates unnecessary potential differences, reducing current flow through power source wirings and decreasing total current consumption while maintaining the ability to scale CAM array capacity.

Inventive Principle:
Principle #35Parameter changes

4Object-generated harmful factors

If the power source wirings are thickened to reduce impedance, then the power-supply noise is reduced, but the manufacturing cost increases

Engineering Contradiction:
Improvepower-supply noiseVSAvoidmanufacturing cost
Core Design Contradiction:
Object-generated harmful factorsVSEase of manufacture

Solution Approach 1:

The patent applies equipotentiality by equalizing the potentials of complementary match lines (MLp and MLn) to the same voltage level (VDD/2) before comparison operations. This is achieved through dedicated equalizer circuits that adjust the potential of each match line to match a reference potential. By maintaining equal potentials before operations and restoring equal potentials after operations, the invention eliminates potential differences that would otherwise cause large current flows, thereby reducing electromagnetic interference and power-supply noise while enabling increased CAM array capacity.

Inventive Principle:
Principle #12Equipotentiality

Data Source

PatentUS8169807B2Content addressable memory device having match line equalizer circuit
Publication Date: 2012.05.01 RENESAS ELECTRONICS CORP
  • US8169807B2 patent drawing
  • US8169807B2 patent drawing
  • US8169807B2 patent drawing

AI summary

In a content addressable memory device, before search operations in two TCAM cells connected to first and second match lines, respectively, a memory controller connects the first match line to a power source and connects the second match line to a ground, and then connects the first and second match lines to each other so as that electric potentials of the first and second match lines are the same as each other.