Serial Flash CAM Cell for High-Density Genome Search
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Solution Overview
Problem
Current content addressable memory (CAM) technologies, such as TCAM and RRAM-based CAM, face challenges in achieving high memory density, low power consumption, and accurate matching for large data searches, particularly in genome analysis, where they struggle with parallel search capabilities and long word search designs.
Innovation Solution
A CAM cell and device design utilizing serially connected flash memory cells with multiple threshold voltages and search voltages to enhance matching accuracy and efficiency, allowing for in-memory searching and data comparison, particularly suited for genome analysis and long word searches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If RRAM-based TCAM with 2T2R structure is used to reduce cell area, then memory density is improved, but matching accuracy deteriorates because RRAM has limited resistor ratio and matching/non-matching statuses are hardly distinguishable
Solution Approach 1:
The patent merges multiple flash memory cells into a single CAM cell structure. Specifically, it combines multiple memory cells with different threshold voltages (e.g., Vt0, Vt1, Vt2, Vt3) into one functional CAM cell unit, allowing parallel comparison of multiple bits while maintaining high matching accuracy through the distinct threshold voltage characteristics of each cell
Solution Approach 2:
The patent utilizes parameter changes by employing flash memory cells with deliberately different threshold voltages. Each memory cell in the merged structure has a unique threshold voltage parameter, enabling the system to distinguish between matching and non-matching states through current threshold detection, thereby achieving high matching accuracy in a compact structure
2Area of stationary object
If FeFET-based TCAM array is used to provide higher on-current/off-current ratio, then memory density is improved, but matching accuracy deteriorates because the on-current/off-current ratio is not high enough for long word search design
Solution Approach 1:
The patent merges multiple flash memory cells into one CAM cell to achieve higher effective current ratio. By combining cells with different threshold voltages in a parallel comparison structure, the system amplifies the current difference between matching and non-matching states, enabling accurate long word search even though individual flash cells have moderate on/off ratios
Solution Approach 2:
The patent segments the comparison function across multiple memory cells with different threshold voltages. Each cell segment handles a specific current threshold level, and their combined output provides multi-level matching accuracy, effectively dividing the matching task into segments that collectively achieve high precision
3Productivity
If conventional TCAM based on SRAM is used to implement parallel searching, then search capability is improved, but memory density deteriorates due to 16 transistors per cell
Solution Approach 1:
The patent replaces the traditional SRAM-based TCAM mechanical structure with a flash memory-based system. Instead of using 16 transistors per cell as in conventional TCAM, the invention uses flash memory cells that leverage electrical charge storage and threshold voltage characteristics, fundamentally substituting the mechanical transistor switching approach with an electrical field-based memory mechanism that achieves higher density
Solution Approach 2:
The patent changes the fundamental operating parameter from transistor count to threshold voltage diversity. By using flash memory cells with different programmed threshold voltages instead of multiple transistors, the system achieves parallel search capability through voltage-level differentiation rather than transistor switching, dramatically reducing cell area while maintaining search functionality
Data Source
AI summary
The application provides a content addressable memory (CAM) cell, a CAM memory device and an operation method thereof, and a method for searching and comparing data. The CAM cell includes a first flash memory cell having a first terminal for receiving a first search voltage; and a second flash memory cell having a first terminal for receiving a second search voltage, a second terminal of the first flash memory cell electrically connected to a second terminal of the second flash memory cell, wherein the first flash memory cell and the second flash memory cell are serially connected; and a storage data of the CAM cell is based on a combination of a plurality of threshold voltages of the first flash memory cell and the second flash memory cell.