In-Memory Search Transistor Pair Encoding Mismatch Distance
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Solution Overview
Problem
Existing in-memory search mechanisms cannot determine the degree of mismatch between stored and search data, limiting their flexibility in matching operations.
Innovation Solution
A memory device and method that utilize a pair of transistors with adjustable threshold voltages and gate biases to encode and compare data, generating an output current related to the mismatch distance between stored and search data, enabling approximate matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an exact matching mechanism is used in the in-memory search operation, then the search accuracy is improved, but the flexibility of matching is worsened because the mechanism cannot determine the degree of mismatch between stored data and search data
Solution Approach 1:
The patent changes the parameter representation by encoding data not as single threshold voltages but as pairs of threshold voltages (first and second threshold voltages) for each memory cell. This dual-parameter encoding enables the system to represent multiple data states and compute mismatch distances, thereby achieving both accurate matching and flexible adaptability for approximate search operations.
2Device complexity
If a single transistor is used to store data, then the device complexity is reduced, but the capability to determine mismatch distance is lost
Solution Approach 1:
The patent segments the data storage function by dividing each stored data value into two separate threshold voltage components (first and second threshold voltages) stored in series-connected transistors. This segmentation allows the system to perform differential comparisons that compute mismatch distances, enabling precise measurement capabilities while maintaining a relatively simple memory cell structure.
Data Source
AI summary
A memory device for in-memory search is provided. The memory device includes a plurality of memory cells, and each of the memory cells stores a stored data and receives a search data, including a first transistor and a second transistor. The first transistor has a first threshold voltage and receives a first gate bias. The second transistor is connected to the first transistor, and the second transistor has a second threshold voltage and receives a second gate bias. The stored data is encoded according to the first threshold voltage and the second threshold voltage, and the search data is encoded according to the first gate bias and the second gate bias. There is a mismatch distance between the stored data and the search data. An output current generated by each of the memory cells is related to the mismatch distance.