Ternary Content Addressable Memory Unit Reducing Charge Sharing
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Solution Overview
Problem
Conventional ternary content addressable memory (TCAM) units face issues with charge sharing between nodes, leading to voltage drops and matching errors during memory operations.
Innovation Solution
The proposed TCAM unit incorporates a specific configuration of inverters and transistors, including a first inverter, second inverter, third inverter, and fourth inverter, along with various transistors, to manage node voltages and prevent charge sharing, utilizing a floating or grounded reference terminal to maintain stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional TCAM node configuration is used, then the circuit design is simpler, but charge sharing causes voltage drops and matching errors
Solution Approach 1:
The TCAM cell is divided into two independent storage nodes (first node and second node), each with its own inverter and transistor configuration. This segmentation isolates the charge storage functions, preventing charge sharing between nodes while maintaining individual node stability, thereby improving matching accuracy without excessive complexity increase
Solution Approach 2:
A reference terminal is introduced as an intermediary element connected to the first wordline. This reference terminal acts as a stable voltage reference that prevents charge sharing effects between nodes by providing a fixed potential reference point, thereby improving reliability while adding only minimal circuit complexity
2Manufacturing precision
If more metal layers are used, then the circuit design becomes more complex, but manufacturing precision improves
Solution Approach 1:
The first wordline serves multiple functions: it connects to the reference terminal, controls the first transistor, and provides a stable reference potential. This multi-functionality reduces the need for additional dedicated metal layers, achieving reliable connections with minimal metal layer usage while maintaining manufacturing precision
Solution Approach 2:
The reference terminal is merged with the first wordline structure, combining the reference potential function with the wordline control function. This merging eliminates the need for separate reference potential metal layers, reducing overall metal layer complexity while maintaining precise connections through the unified structure
Data Source
AI summary
A ternary content addressable memory unit includes a first inverter, a second inverter, a third inverter, a fourth inverter, a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, and an eighth transistor. The first inverter includes an input terminal, and an output terminal coupled to a first node. The second inverter includes an input terminal coupled to the first node and an output terminal coupled to the input terminal of the first inverter. The third inverter includes an input terminal coupled to a second node and an output terminal. The fourth inverter includes an input terminal coupled to the output terminal of the third inverter and an output terminal coupled to the second node.