Semiconductor Device Match Line Precharging for Power Reduction
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Solution Overview
Problem
TCAM devices consume a large amount of electrical power due to the need for precharging match lines before search operations, which is inefficient and increases power consumption.
Innovation Solution
A semiconductor device with multiple search memory cells, match lines, sub-ground lines, and amplifiers is designed, where match lines and sub-ground lines are precharged to specific potentials before a search, and when search data is mismatched, the match lines are set to an intermediate potential, reducing the power required for precharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If match lines are precharged to a high potential before search operations, then the search operation can be performed, but the power consumption increases significantly
Solution Approach 1:
The patent divides the traditional single precharge operation into two distinct phases: a first precharge phase that charges match lines to an intermediate potential, and a second precharge phase that charges them to the final high potential. This segmentation allows the system to perform search operations from the intermediate potential state, avoiding the need to fully charge all match lines to high potential before every search, thereby reducing overall power consumption while maintaining search functionality.
Solution Approach 2:
The patent introduces dynamic control of match line potentials through selective coupling with sub-ground lines. During search operations, mismatched match lines are dynamically coupled to sub-ground lines to maintain them at an intermediate potential rather than fully charging them to high potential. This dynamic adjustment of potential levels based on match/mismatch status reduces the energy required for precharging while ensuring that matched lines maintain the necessary high potential for reliable detection.
2Measurement precision
If match lines are set to low potential for mismatched data, then the search result can be determined, but the power consumption increases due to charging and discharging operations
Solution Approach 1:
The patent prepares sub-ground lines in advance by charging them to a potential higher than ground potential but lower than the high potential of matched match lines. This beforehand cushioning creates an intermediate potential state that serves as a buffer for mismatched match lines. When a mismatch is detected, the match line can be coupled to the pre-prepared sub-ground line, transitioning to the intermediate potential without requiring a full discharge to ground and subsequent recharge, thereby reducing the energy loss associated with complete charging and discharging cycles.
Data Source
AI summary
A semiconductor device includes a plural search memory cells, a plural match lines, a plural sub-ground lines, and a plural amplifiers. The search memory cells are disposed in a matrix form. The match lines are disposed in association with respective memory cell rows and used to determine whether search data matches data stored in the search memory cells. The sub-ground lines are disposed in association with respective memory cell rows. The amplifiers are disposed in association with respective memory cell rows to amplify the potentials of the match lines. The match lines and the sub-ground lines are respectively precharged to a first potential and a second potential before a data search. When the search data is mismatched, the match lines are electrically coupled to associated sub-ground lines through the search memory cells and set to an intermediate potential that is intermediate between the first potential and the second potential.