Analog CAM Circuit Encoding Arbitrary Range Segments
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Solution Overview
Problem
Existing analog content addressable memory (aCAM) circuit implementations are inefficient in searching arbitrary segments of ranges, requiring substantial area to encode the complement of the range, making it difficult to search outside or within multiple disjoint ranges effectively.
Innovation Solution
The implementation of aCAM circuits using non-volatile components like memristors and transistors, with specific voltage divider circuits and pull-down or pass gate configurations, allows for efficient searching outside or within multiple disjoint ranges by tuning conductances to establish upper and lower voltage bounds, enabling flexible and efficient encoding of arbitrary range segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing aCAM circuit implementations are used to search arbitrary segments of ranges, then searching capability is provided, but circuit area increases substantially due to encoding the complement of the range
Solution Approach 1:
The patent inverts the traditional approach by encoding the range to be searched directly instead of encoding its complement. This allows the aCAM circuit to search for values within a specific range [Vmin, Vmax] without requiring substantial area to represent all values outside that range. The inversion principle transforms the problem from searching 'outside a range' to searching 'within a range' by redefining what is encoded in the memory cells.
Solution Approach 2:
The patent applies local quality by using different encoding strategies for different parts of the value space. Instead of uniformly encoding all possible values, the circuit uses specific voltage divider configurations (with resistors R1, R2, R3) to encode only the relevant range boundaries. This allows efficient representation of arbitrary range segments by focusing resources on the local properties of the desired search space rather than the entire value space.
2Adaptability or versatility
If conventional aCAM circuits encode complement of range, then range searching is enabled, but device complexity increases
Solution Approach 1:
The patent simplifies device complexity by inverting the encoding approach. Instead of complex logic to encode and search for values outside a range, the circuit directly encodes the range boundaries (Vmin, Vmax) using voltage dividers and compares input values against these boundaries. This inversion reduces the logical complexity of the circuit while maintaining full range searching capability.
Solution Approach 2:
The patent segments the range searching function into independent voltage divider circuits, each responsible for comparing against specific boundaries (Vmin, Vmax). This segmentation allows the complex range searching task to be divided into simpler, modular comparison operations that can be implemented with basic circuit elements, reducing overall device complexity.
3Quantity of substance
If aCAM circuits use traditional encoding methods, then basic storage is achieved, but efficiency in searching arbitrary segments decreases
Solution Approach 1:
The patent changes the physical parameters of the aCAM circuit by using voltage-based encoding instead of traditional binary encoding. By representing range boundaries as voltage levels (Vmin, Vmax) and using voltage divider circuits with adjustable resistors, the system achieves efficient searching of arbitrary segments. This parameter change from digital to analog representation enables continuous range searching without the efficiency loss associated with discrete binary comparisons.
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 approach significantly reduces circuit complexity and increases efficiency in searching arbitrary segments of ranges, enabling applications in access control lists, network routing, and decision trees with improved performance.
Implementation Method 1
a first voltage divider circuit of the aCAM cell and a second voltage divider circuit of the aCAM cell
Data Source
AI summary
Systems, devices, circuits, methods, and non-transitory computer readable media that enable storing and searching arbitrary segments of ranges of analog values are disclosed. Various analog content addressable memory (aCAM) circuit implementations having the capability to store and search outside of a range of values, within any of multiple disjoint ranges, or outside of multiple ranges are disclosed. The disclosed aCAM circuit implementations make searching for complex input features more flexible and efficient, thereby yielding a technological improvement over conventional solutions. In some implementations, an aCAM may include multiple pull-down transistors connected in series to a match line that is pre-charged, in which case, the aCAM detects a match if the match line is not discharged by the pull-down transistors, which occurs if at least one pull-down transistor is in an OFF state. In other implementations, an aCAM includes pass gates connected to a match line to detect a match.