Multi-stage Content Addressable Memory Power Optimization

Solution Overview

Problem

Content-addressable memories (CAMs) face high power consumption and peak currents due to their parallel design, limiting their applicability in various applications, despite techniques like segment-wise comparison and multi-stage architectures that reduce power consumption.

Innovation Solution

A multi-stage CAM architecture with different power regimes across stages, where the first stage operates at lower voltage and power for frequent comparisons, and subsequent stages at higher voltage and power if a match is found, along with varying pre-charge voltages and clock rates to optimize power usage and speed.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If parallel search architecture is used to achieve fast search speed, then search speed is improved, but power consumption increases

Engineering Contradiction:

Improvesearch speedVSAvoidpower consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The CAM is divided into multiple stages, with each stage handling a portion of the search. The first stage performs initial comparisons at lower power, and only if a match is found does the second stage activate to complete the search. This segmentation allows the system to maintain fast search capability while reducing average power consumption by not always activating all parallel search resources.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic power management where the second stage is conditionally activated based on match detection from the first stage. The clock signal to the second stage is enabled only when needed, creating a dynamic operation mode that adapts power consumption to actual search requirements while preserving fast search performance when matches occur.

Inventive Principle:

Principle #15Dynamics

2Use of energy by moving object

If multi-stage architecture with conditional activation is used to reduce power consumption, then power consumption is reduced, but device complexity increases

Engineering Contradiction:

Improvepower consumptionVSAvoiddevice complexity

Core Design Contradiction:

Use of energy by moving objectVSDevice complexity

Solution Approach 1:

The CAM is divided into multiple stages, with each stage handling a portion of the search. The first stage performs initial comparisons at lower power, and only if a match is found does the second stage activate to complete the search. This segmentation allows the system to maintain fast search capability while reducing average power consumption by not always activating all parallel search resources.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements dynamic power management where the second stage is conditionally activated based on match detection from the first stage. The clock signal to the second stage is enabled only when needed, creating a dynamic operation mode that adapts power consumption to actual search requirements while preserving fast search performance when matches occur.

Inventive Principle:

Principle #15Dynamics

3Use of energy by moving object

If different pre-charge voltages are applied to different stages to optimize power usage, then power consumption is reduced, but manufacturing precision requirements increase

Engineering Contradiction:

Improvepower consumptionVSAvoidvoltage precision

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

Different pre-charge voltages are applied to different stages of the CAM. The first stage uses a first pre-charge voltage optimized for its comparison requirements, while the second stage uses a second pre-charge voltage optimized for its specific needs. This local optimization of voltage characteristics reduces overall power consumption while maintaining reliable operation through stage-specific parameter tuning.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS11342022B2Low-power multi-stage/multi-segment content addressable memory device

Publication Date: 2022.05.24 MEDIATEK SINGAPORE PTE LTD

AI summary

Multi-stage content addressable memory devices are described. Some embodiments relate to memory devices including a plurality of rows of memory cells, multiple match lines and multiple pre-charge circuits. A first row of the plurality of rows includes a first segment and a second segment. The first segment may include a first subset of the memory cells of the first row and the second segment may include a second subset of the memory cells of the first row. The first match line is coupled to the memory cells of the first subset, and the second match line is coupled to the memory cells of the second subset. The first pre-charge circuit is configured to pre-charge the first match line to a first pre-charge voltage, and the second pre-charge circuit is configured to pre-charge the second match line to a second pre-charge voltage different from (e.g., greater than) the first pre-charge voltage.