Memory Device Read Voltage Control for Speed and Precision
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Solution Overview
Problem
Current memory devices face challenges in reducing the time required for read operations due to inefficiencies in voltage control, particularly in accurately and rapidly applying voltages to word lines, which affects the speed and reliability of data retrieval.
Innovation Solution
A memory device and method that involve a memory block with multiple word lines, a peripheral circuit for performing read operations by applying a read voltage to a selected word line and a first pass voltage to adjacent unselected word lines, with control logic that adjusts the read voltage and pass voltage based on variations, ensuring the pass voltage variation is less than the read voltage variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the read voltage is rapidly adjusted to reduce read operation time, then the read speed is improved, but the voltage control precision deteriorates
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the read voltage level based on the program state of memory cells. Different read voltages are used for different threshold voltage ranges, allowing rapid voltage transitions while maintaining precise control through state-dependent voltage selection. This resolves the contradiction by making voltage control precision adaptive rather than static.
Solution Approach 2:
The patent implements dynamics by using a multi-level voltage system where the read voltage can transition between multiple discrete levels (e.g., first read voltage for high threshold voltage cells, second read voltage for low threshold voltage cells). This dynamic voltage adjustment enables fast read operations while maintaining precision through the structured voltage hierarchy.
2Measurement precision
If the pass voltage is adjusted to match read voltage variations, then the voltage control precision is improved, but the read operation time increases
Solution Approach 1:
The patent applies local quality by differentiating the voltage adjustment strategy between selected and unselected word lines. The pass voltage applied to unselected word lines is adjusted with less variation than the read voltage on the selected word line. This localized differential approach maintains sufficient voltage control precision for interference suppression while minimizing the time penalty associated with synchronized voltage adjustments.
3Measurement precision
If the read voltage is decreased for multi-level cell reading, then the measurement precision for different program states is improved, but the reliability of data retrieval deteriorates
Solution Approach 1:
The patent implements feedback by using the sensed data from memory cells to determine the appropriate read voltage level for subsequent operations. The system adjusts read voltages based on program state information, creating a feedback loop that improves measurement precision for distinguishing different program states while maintaining reliability through adaptive voltage selection based on actual cell states.
Solution Approach 2:
The patent applies parameter changes by transitioning from a single read voltage level to multiple read voltage levels corresponding to different program states. This parameter differentiation enables precise discrimination between program states (improving measurement precision) while the structured voltage levels maintain reliability by ensuring adequate voltage margins for each state.
Data Source
AI summary
Provided herein may be a memory device and a method of operating the same. The memory device may include a memory block including a plurality of memory cells that are coupled to a plurality of word lines, a peripheral circuit configured to perform a read operation by applying a read voltage to a selected word line, among the plurality of word lines, and applying a first pass voltage to target word lines, wherein the target word lines are adjacent to the selected word line, among unselected word lines other than the selected word line, and a control logic configured to decrease the read voltage based on a read voltage variation and to decrease the first pass voltage based on a pass voltage variation when the read voltage decreases, wherein the pass voltage variation is less than the read voltage variation.