Memory Controller Read Voltage Estimation via Statistical Analysis
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Solution Overview
Problem
Memory systems face challenges in accurately distinguishing between adjacent threshold voltage distributions due to changes in channel characteristics, leading to increased read errors and potential failure of error correction decoding.
Innovation Solution
A memory system and method that estimates an optimum read voltage based on standard deviations and average threshold voltages of adjacent threshold voltage distributions, using probability density functions and inverse Q-function values to calculate the standard deviation and average threshold voltages, allowing for accurate differentiation between memory cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional read voltage estimation methods are used, then the operation is simple, but the ability to distinguish adjacent threshold voltage distributions deteriorates leading to read errors
Solution Approach 1:
The system performs preliminary actions by calculating standard deviations and average threshold voltages of multiple threshold voltage distributions before determining the optimal read voltage. This preparatory statistical analysis enables accurate distinction between adjacent distributions while maintaining systematic operation flow
Solution Approach 2:
The patent introduces probability density functions as intermediary mathematical tools to model and analyze threshold voltage distributions. These functions serve as mediators between raw threshold voltage data and the final read voltage determination, enabling precise distinction through statistical characterization
2Reliability
If fixed read voltage is used, then the operation is simple, but reliability deteriorates when channel characteristics change
Solution Approach 1:
The system implements dynamic read voltage determination by continuously analyzing threshold voltage distribution characteristics and adjusting the read voltage accordingly. This dynamic approach adapts to changing channel characteristics, maintaining high reliability through real-time statistical analysis of standard deviations and average voltages
Solution Approach 2:
The patent employs feedback mechanisms where the calculated statistical parameters (standard deviations and average threshold voltages) feed back into the read voltage determination process. This closed-loop approach ensures that read voltage settings continuously adapt to actual threshold voltage distribution states, improving decoding reliability under varying conditions
Data Source
AI summary
A memory system may include a memory device and a memory controller. The memory device may include memory cells. The memory controller may estimate and use an read voltage to distinguish one or more memory cells corresponding to a first threshold voltage distribution from one or more memory cells corresponding to a second threshold voltage distribution, the read voltage being estimated based on standard deviations and average threshold voltages of the first and the second threshold voltage distributions and probability density functions corresponding to the first and the second threshold voltage distributions, respectively. The memory controller may be structured and operable to calculate the standard deviation of the first threshold voltage distribution, based on a first probability area distinguished by a first target read voltage, a second probability area distinguished by a second target read voltage, and inverse Q-function values corresponding to the first and the second probability areas.