Memory Controller Tracking Process for Decoding Accuracy
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Solution Overview
Problem
Current memory systems face inefficiencies in decoding processes due to limitations in error correction capabilities and the time required for decoding operations, particularly when dealing with multi-level cell configurations and threshold voltage distributions that change over time.
Innovation Solution
A memory system and control method that includes a memory controller capable of performing a tracking process by shifting read voltages to estimate likelihood information for bit values, allowing for a second decoding process using this information to improve decoding accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a first decoding process is performed on read data using a first read voltage, then decoding can be attempted quickly, but decoding accuracy is insufficient when threshold voltage distributions have changed
Solution Approach 1:
The patent performs a track process before the second decoding process to update threshold voltage distribution information. This preliminary action prepares accurate reference data that enables the subsequent decoding to achieve high accuracy without requiring extensive trial-and-error iterations, thus resolving the contradiction between decoding accuracy and decoding time.
Solution Approach 2:
The patent implements a feedback mechanism where the track process continuously updates threshold voltage distribution information based on actual read data. This feedback loop allows the system to adapt to changes in memory characteristics over time, improving decoding accuracy while maintaining efficiency by using updated reference data in the second decoding process.
2Reliability
If error correction coding is applied to protect stored data, then data reliability is improved, but the decoding process becomes more complex and time-consuming
Solution Approach 1:
The track process performs preliminary analysis of threshold voltage distributions before the main decoding operation. By preparing updated reference information in advance, the system simplifies the subsequent second decoding process, making it less complex while maintaining high data reliability through accurate error correction.
3Measurement precision
If multiple read voltages are used in a track process to obtain likelihood information, then decoding accuracy is improved, but the time required for the tracking process increases
Solution Approach 1:
The track process using multiple read voltages is performed as a preliminary step before the main decoding operation. Although this initial process takes time, it establishes accurate threshold voltage distribution information that significantly reduces the time required for subsequent decoding operations, achieving overall time efficiency while maintaining high accuracy.
Data Source
AI summary
A memory system includes a nonvolatile memory including memory cells, and a memory controller. The memory controller is configured to read first data through application of a first read voltage to each of the memory cells, perform a first decoding process with respect to the first data, when the first decoding process fails, perform a tracking process. The tracking process includes reading second data indicating a threshold voltage level of each of the memory cells through application of a plurality of second read voltages to each of the memory cells, and obtaining, with respect to each of the memory cells, likelihood information using the second data. The second read voltages are shifted by a predetermined amount. The memory controller is further configured to perform a second decoding process with respect to the second data using the likelihood information.