Sense Circuit Dual-Path Threshold Voltage Gap Memory State Detection

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Solution Overview

Problem

In memory systems, charge loss in memory cells causes threshold voltage shifts, making it difficult to determine the logical state of memory cells over time, especially as the read window bandwidth between adjacent threshold voltage distributions narrows, leading to increased difficulty in distinguishing between logical states during read operations.

Innovation Solution

A sense circuit with two sensing paths is introduced, where one path has a built-in threshold voltage gap, eliminating the need for an additional boost voltage while generating the required histograms to determine the local minima, thereby reducing read operation time and increasing the voltage sensing range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a single sensing path is used to sense memory cell states, then the device complexity is reduced, but the measurement precision deteriorates due to narrowed read window bandwidth

Engineering Contradiction:

Improvesensing path structureVSAvoidstate distinction capability

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The sensing operation is segmented into two parallel sensing paths, each with different threshold voltage characteristics. The first sensing path uses a first threshold voltage to sense a first state, while the second sensing path uses a second threshold voltage to sense a second state. This segmentation allows simultaneous acquisition of multiple state information without requiring sequential operations, thereby maintaining measurement precision while managing device complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a threshold voltage dimension by creating sensing paths with different threshold voltage levels. Instead of using a single sensing path with variable voltage adjustments, the invention adds a dimensional aspect by parallelizing sensing at multiple threshold voltage levels, effectively expanding the sensing capability from one-dimensional (single threshold) to multi-dimensional (multiple thresholds simultaneously).

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Measurement precision

If additional boost voltage is applied to sense memory cell states, then the measurement precision is improved, but the loss of time increases due to extended read operation duration

Engineering Contradiction:

Improvestate distinction capabilityVSAvoidread operation time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The sensing paths are pre-configured with different threshold voltage characteristics before the sensing operation begins. This preliminary configuration eliminates the need for dynamic voltage adjustments during the sensing process, allowing immediate sensing at the appropriate threshold levels and reducing the time required for read operations while maintaining measurement precision.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The dual sensing paths operate simultaneously and continuously during the read operation, eliminating the need for sequential sensing steps or repeated voltage boosting cycles. This continuous parallel operation maintains measurement precision across multiple states while significantly reducing the total time required compared to sequential sensing approaches.

Inventive Principle:

Principle #20Continuity of useful action

3Measurement precision

If the read window bandwidth is maintained for accurate state sensing, then the measurement precision is improved, but the difficulty of detecting and measuring increases due to charge loss effects

Engineering Contradiction:

Improvestate distinction capabilityVSAvoidstate detection complexity

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

Each sensing path is designed with specific local quality characteristics, namely different threshold voltage levels optimized for detecting particular states. The first sensing path is optimized for detecting states within a first voltage range, while the second sensing path is optimized for detecting states within a second voltage range. This local optimization reduces the overall difficulty of detection by dividing the measurement task into specialized sub-tasks.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the threshold voltage parameter of the sensing paths to accommodate charge loss effects. By setting different threshold voltage levels in the parallel sensing paths, the system can accurately detect memory cell states even when charge loss causes threshold voltage shifts, thereby maintaining measurement precision while simplifying the detection process compared to single-path adaptive methods.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11557351B2Sense circuit to sense two states of a memory cell

Publication Date: 2023.01.17 MICRON TECHNOLOGY INC

AI summary

A device includes a memory array and a sense circuit coupled with the memory array. The sense circuit includes a sense node coupled with a data line of the memory array. A first sensing path includes a first transistor having a first gate coupled with the sense node. A second sensing path includes a second transistor having a second gate coupled with the sense node. A first threshold voltage of the first transistors differs from a second threshold voltage of the second transistor by a threshold voltage gap.