Ternary Content Addressable Memory Segmented Cell Strings
Solution Overview
Problem
Ternary content addressable memories using inverse-OR flash memory cell pairs face issues with high voltage requirements and incorrect search results due to excessive current generation when multiple source line switches are turned on, leading to inefficient search operations.
Innovation Solution
The implementation of paired memory cell strings with selection switches controlled by search signals, where only one memory cell string provides current for a match and the other for a mismatch, effectively managing current flow to prevent incorrect search results and enhance search bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If inverse-OR flash memory cell pairs are used with multiple source line switches turned on, then search bandwidth is increased, but excessive current is generated causing incorrect search results
Solution Approach 1:
The memory cell array is divided into multiple independent memory cell strings (first memory cell string, second memory cell string, etc.), each with its own selection switch. This segmentation allows individual control of current paths, enabling multiple strings to be searched simultaneously without excessive current accumulation, thus increasing search bandwidth while maintaining result accuracy.
Solution Approach 2:
The selection switches (first memory cell string selection switch, second memory cell string selection switch) are dynamically controlled by search signals to enable or disable specific memory cell strings based on the search operation requirements. This dynamic control allows flexible adjustment of active string数量, optimizing search bandwidth while preventing excessive current generation.
2Power
If higher voltages are applied for read operations in inverse-OR flash memory cell architecture, then read capability is improved, but power consumption and device stress increase
Solution Approach 1:
By segmenting the memory into multiple independently controllable cell strings with dedicated selection switches, the patent enables selective activation of only the necessary memory strings during read operations. This reduces the overall power consumption and device stress compared to activating all strings with high voltage simultaneously, while maintaining adequate read capability for the active strings.
Data Source
AI summary
A ternary content addressable memory, disposed in a stacked memory device, includes a first memory cell string and a second memory cell string. The first memory cell string is coupled between a matching line and a first source line and receives multiple first word line signals. The first memory cell string has a first memory cell string selection switch controlled by a first search signal. The second memory cell string is coupled between the matching line and a second source line and receives multiple second word line signals. The second memory cell string has a second memory cell string selection switch controlled by a second search signal.