Memory Controller Read Voltage Correction for NAND Flash Temperature Variations
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Solution Overview
Problem
Existing memory controllers face challenges in obtaining appropriate read voltages for non-volatile memory, particularly NAND flash memory, due to varying physical properties with temperature changes, leading to potential errors in data retrieval.
Innovation Solution
A memory controller with a temperature measurement unit, distribution acquiring processor, detector, decoder, and temperature correcting processor that acquires and corrects read voltages based on temperature data, using specific correction expressions to adjust read voltages and minimize errors across different threshold voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature correction is performed using related art methods, then the read voltage detection attempts to account for temperature variations, but it is not possible to obtain an appropriate read voltage due to the complexity of temperature-dependent threshold voltage shifts
Solution Approach 1:
The patent segments the threshold voltage distribution into multiple distinct levels (first threshold voltage level, second threshold voltage level, third threshold voltage level) and applies separate correction expressions to each level. This segmentation allows the system to handle the complexity of temperature-dependent voltage shifts by treating each threshold level independently with its own correction formula, rather than attempting a single complex correction for all levels.
Solution Approach 2:
The patent changes the correction parameters based on temperature conditions by using different correction expressions (first correction expression, second correction expression, third correction expression) for different threshold voltage levels. Each correction expression contains temperature-dependent parameters that are specifically tuned for its corresponding threshold level, allowing the system to adapt to temperature variations while maintaining accuracy across all threshold levels.
2Device complexity
If a single temperature correction method is applied to all threshold voltage levels, then the correction process is simplified, but the read voltage accuracy deteriorates for specific threshold levels
Solution Approach 1:
The patent applies local quality by using different correction expressions specifically tailored to each threshold voltage level's characteristics. The first correction expression is applied to the first threshold voltage level, the second correction expression to the second threshold voltage level, and the third correction expression to the third threshold voltage level. This localized approach ensures that each threshold level receives the most appropriate correction for its specific temperature-dependent behavior, maximizing read voltage precision for each level.
3Productivity
If no temperature correction is applied, then the device operation is simpler and faster, but read errors increase due to temperature variations in memory cell properties
Solution Approach 1:
The patent performs preliminary temperature correction by detecting the threshold voltage distribution shape at different temperature levels and establishing correction expressions before actual data reading operations. The system pre-determines the appropriate correction expression to apply based on the detected threshold voltage characteristics, allowing for rapid correction during read operations without requiring complex real-time calculations, thus maintaining both speed and accuracy.
Data Source
AI summary
According to one embodiment, a temperature of a non-volatile memory or an ambient temperature of the non-volatile memory is acquired. A distribution of a threshold voltage, which is corrected according to the acquired temperature, is acquired from the non-volatile memory. Read voltages related to the reading of data are detected from the distribution. Error correction is performed for data read from the non-volatile memory, using the read voltages. The detected read voltages are separately corrected on the basis of the acquired temperature when the error correction has failed.