Ternary Content Addressable Memory Bit-Line Search Architecture
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Solution Overview
Problem
Traditional NAND-type ternary content addressable memory (TCAM) systems face difficulties in handling increasing data lengths due to the limited number of word lines, which restricts their ability to process high-resolution images and precise floating-point values effectively.
Innovation Solution
A ternary content addressable memory device and operation method are introduced, featuring a memory array with M first and second bit-lines, M first and second source lines, N word lines, and a control circuit. The memory array includes M*N memory cells, each with two transistors, and a sensing circuit that generates sensing currents in response to search voltages and threshold voltages, allowing for efficient data search operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If traditional NAND-type TCAM uses word lines as search lines, then the structure is simple, but the allowable data length is limited by the quantity of word lines
Solution Approach 1:
The patent transitions from using word lines as search lines to using bit lines as search lines, fundamentally changing the dimensional approach. This allows the search capability to scale with the number of bit lines rather than word lines, enabling handling of longer data lengths while maintaining structural simplicity through the bit-line-based architecture
Solution Approach 2:
The memory array is segmented into multiple bit lines (first bit lines and second bit lines) that can be independently controlled and searched. This segmentation allows parallel search operations across multiple bit lines, increasing the effective data length处理能力 without proportionally increasing the number of word lines
2Length of moving object
If the quantity of word lines is increased to handle longer data, then the data length capability improves, but the device complexity increases
Solution Approach 1:
Instead of increasing the number of word lines to handle longer data (the conventional approach), the patent inverts the approach by using bit lines as search lines. This inversion allows the search capability to be determined by the number of bit lines, which can be kept manageable while still supporting long data lengths through parallel bit line operations
3Length of moving object
If bit lines are used as search lines instead of word lines, then the data length capability improves, but the sensing current generation and detection complexity increases
Solution Approach 1:
The patent introduces sensing current generation as an intermediary mechanism between the bit line search voltages and the data storage threshold voltages. By generating sensing currents that flow through the memory cells based on the difference between search voltages and threshold voltages, the system transforms the comparison operation into a measurable current signal, facilitating easier detection of match/mismatch conditions
Solution Approach 2:
The patent replaces direct voltage comparison detection with a current-based sensing mechanism. Instead of directly measuring voltage differences which can be difficult to detect, the system substitutes this with generating and detecting sensing currents that are proportional to the voltage differences, making the detection process more reliable and easier to implement
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 solution enables the memory device to perform efficient data search operations by generating sensing currents that represent data match/mismatch comparisons, effectively handling longer data lengths and improving the processing of high-resolution images and precise floating-point values.
Implementation Method 1
an m-th first sensing current is selectively generated in response to the first search voltage and a threshold voltage of the first transistor. An m-th second sensing current is selectively generated in response to the second search voltage and a threshold voltage of the second transistor
Data Source
AI summary
A memory device and associated operation method are provided. The operation method is applied to the memory device to determine whether a search input and in-memory data are matched. The memory device includes a memory array and a control circuit, and the memory array includes M*N memory cells. The operation method includes the following steps. A select voltage is applied to an n-th word line. A pass-through voltage is applied to (N−1) word lines. A first search voltage is applied to an m-th first bit-line, and a second search voltage is applied to an m-th second bit-line. An m-th first sensing current and an m-th second sensing current bit are selectively generated. Then, a sensing circuit in the control circuit generates a sensing circuit output. The sensing circuit output represents whether the m-th first sensing current and the m-th second sensing current are generated.