Memory Search Circuit Using String Select Line Bit Encoding
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Solution Overview
Problem
Existing memory devices require two word line signals to carry one search bit, limiting the length of search data.
Innovation Solution
A memory device and method that uses a tunable string select line signal to carry a search bit, allowing a single signal to represent logic values 0 or 1, and employs switch elements with different threshold voltage levels to compare search and stored data bits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If two word line signals are used to carry one search bit, then the search data can be carried, but the length of search data is limited
Solution Approach 1:
The patent changes the voltage parameter of the string select line signal to encode search bits. By using different voltage levels (first voltage level for logic 0, second voltage level for logic 1), a single string select line can carry one search bit, doubling the effective search data length compared to using two separate word line signals.
Solution Approach 2:
The string select line is made multi-functional by enabling it to carry search data in addition to its traditional function of selecting memory strings. This allows the same signal line to serve multiple purposes: string selection and search data transmission, thereby reducing the total number of signal lines needed.
2Measurement precision
If switch elements with different threshold voltage levels are used for comparison, then matching and mismatching conditions can be distinguished, but the device structure becomes more complex
Solution Approach 1:
The patent applies local quality by giving different threshold voltage characteristics to different switch elements. Specifically, one switch element has a first threshold voltage level while another has a second threshold voltage level, allowing them to respond differently to the same control signal and thereby encode comparison results.
Solution Approach 2:
The patent replaces traditional complex comparison circuitry with a simplified system using switch elements and voltage level detection. The comparison between search data and stored data is achieved through voltage level transitions and detection, substituting mechanical or electronic comparison circuits with a more efficient voltage-based approach.
Data Source
AI summary
An operating method of a memory device is provided. The operating method includes: carrying a first search bit by a first string select line signal; controlling a first switch element by the first string select line signal; storing a first data bit by second and third switch elements; and comparing the first search bit and the first data bit to generate a first bit line signal. In response to the first search bit having a first logic value, the first string select line signal has first and second voltage levels in order, in response to the first search bit having a second logic value, the first string select line signal has the second and first voltage levels in order, the second voltage level is different from the first voltage level, and the first, second and third switch elements are coupled in series.