Static CAM Summary Circuit Without Pre-Charge Match Lines
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Solution Overview
Problem
Dynamic Content-Addressable Memories (CAMs) are slow, prone to noise, cause timing issues, and require additional circuitry and high power due to dynamic match line charging and discharging, leading to current leakages and weak capacitive coupling.
Innovation Solution
The implementation of a summary circuit with multiple levels of logic gates, including NAND and NOR gates, that eliminates the need for pre-charge circuitry, allowing for higher frequency operation and efficient data lookup without current leakage, by using transistors to manage current flow based on input logic states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If dynamic match line charging and discharging is used in CAM, then data lookup function is achieved, but operation speed decreases and timing issues occur
Solution Approach 1:
The patent extracts and removes the pre-charge circuitry from the CAM cell design, eliminating the need for dynamic match line charging and discharging operations. This extraction of the pre-charge function resolves the contradiction by enabling faster operation speeds while reducing circuitry complexity and timing issues associated with dynamic charging/discharging cycles.
2Use of energy by moving object
If pre-charge circuitry is used in dynamic CAM, then match line operation is enabled, but power consumption increases
Solution Approach 1:
The patent removes the pre-charge circuitry that was responsible for high power consumption in dynamic CAM operations. By extracting this power-intensive component, the invention achieves lower power consumption while maintaining match line operation through alternative static logic gate-based comparison mechanisms that do not require continuous charging and discharging cycles.
3Reliability
If dynamic match line is used in CAM, then data comparison is achieved, but current leakage occurs
Solution Approach 1:
The patent converts the harmful effect of dynamic match line current leakage into a benefit by transitioning to a static logic gate-based comparison system. The static nature of the new design eliminates continuous charging and discharging operations that caused current leakage, thereby improving reliability of data comparison while reducing energy loss through the elimination of the dynamic match line mechanism.
4Device complexity
If pre-charge circuitry is included in CAM, then match line initialization is achieved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the pre-charge circuitry from the CAM design, thereby reducing device complexity and making manufacturing simpler. The removal of this additional circuitry reduces the number of components that need to be manufactured and assembled, directly improving ease of manufacture while maintaining data comparison functionality through the static logic gate approach.
Data Source
AI summary
A memory includes a plurality of content-addressable memory (CAM) cells and a summary circuit associated with the plurality of CAM cells. The summary circuit includes a first level of logic gates and a second level of logic gates. The first level of logic gates have inputs each configured to receive an output of a corresponding one of the plurality of CAM cell. The second level of logic gates have inputs each configured to receive an output of a corresponding one of the first level of logic gates.