Semiconductor Memory Device Match Line Stabilization
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Solution Overview
Problem
In high-capacity ternary content-addressable memory (TCAM) devices, the potential variation of the match line due to coupling capacitance between the match line and search line complicates accurate data search, especially as memory capacity increases, making precise data search operations challenging.
Innovation Solution
A semiconductor memory device design featuring a matrix arrangement of memory cells with a bit line pair, word lines, match lines, and search line pairs, where the search line driver precharges the search line pair to an intermediate voltage, allowing one search line to be driven to the power supply voltage and the other to ground, counterbalancing potential variations on the match line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the memory capacity of TCAM is increased, then the storage capability is improved, but the potential variation of the match line due to coupling capacitance increases, degrading search accuracy
Solution Approach 1:
The search line is divided into two separate search lines (search line 1 and search line 2) that are driven to complementary voltages. This segmentation allows the coupling capacitance effects on the match line to be differentiated and handled separately, enabling independent optimization of each search line's driving conditions to counteract the potential variation caused by increased memory capacity.
Solution Approach 2:
The patent changes the voltage parameters of the search lines by precharging them to intermediate voltages (e.g., 1/2 VDD) rather than standard logic levels. This parameter change allows the search lines to drive the match line with controlled voltage transitions that compensate for coupling capacitance effects, maintaining search accuracy even as memory capacity increases.
2Quantity of substance
If the number of memory cells coupled to a match line is increased, then the memory capacity is improved, but the potential variation of the match line becomes larger, making data search determination difficult
Solution Approach 1:
The patent introduces counterweight mechanisms by providing separate search lines that drive the match line with opposing voltage transitions. The complementary voltage driving (one search line to VDD, the other to ground) creates counterbalancing effects that offset the cumulative coupling capacitance from increased memory cells, stabilizing the match line potential despite higher memory capacity.
Solution Approach 2:
The search lines are precharged to intermediate voltages before the actual search operation. This preliminary action prepares the search lines to deliver controlled voltage transitions that compensate for the potential variation caused by coupling capacitance from multiple memory cells, ensuring stable match line potential throughout the search process.
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
This configuration stabilizes the match line potential, enabling high-accuracy data search operations even with increased memory capacity by counteracting the effects of coupling capacitance, thus improving search accuracy and reducing power consumption.
Implementation Method 1
there is possibility that the potential of the match line varies by being affected by coupling capacitance between the match line and the search line to transfer search data
Data Source
AI summary
A semiconductor memory device capable of a high-accuracy data search is provided. Each of the memory cells can hold two bits of information and includes a first cell and a second cell. The semiconductor memory device also includes a match line and a search line pair to transfer search data. The semiconductor memory device further includes a logic operation cell to drive the match line based on comparison results between information held in the first and the second cell and search data transferred by the search line pair and a search line driver to drive the search line pair. In a state with the search line pair precharged to a third voltage between a first voltage and a second voltage, the search line driver drives, according to the search data, one and the other search line included in the search line pair to the first and the second voltage, respectively.