Flash Memory Read-Voltage Search Using Linear Regression
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Solution Overview
Problem
Existing data storage devices face issues with voltage drift leading to increased error rates and instability, resulting in incorrect read voltages and reduced decoding success rates due to the limitations of error correction units.
Innovation Solution
A data storage device employing a linear regression model to search for optimal read voltages by analyzing bit patterns across multiple read voltages, using a calculation circuit to determine a coefficient matrix and select the optimal voltage for error correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple reread voltages are attempted to correct errors, then the success rate of decoding can be increased, but the process complexity and time consumption increase significantly
Solution Approach 1:
The patent performs preliminary actions by conducting multiple read operations at different voltages before attempting error correction. The system reads the same data at multiple voltages, collects soft information from each read, and combines this information before decoding. This preliminary gathering of multiple voltage readings provides richer information for the decoder, improving success rates without requiring multiple separate correction attempts.
Solution Approach 2:
The patent introduces soft information as an intermediary between the read operations and the decoder. Instead of directly attempting correction with hard decisions, the system converts read results into soft information (probability metrics) that captures uncertainty and quality of each bit. This intermediary representation allows the decoder to make more informed decisions, improving reliability while maintaining process efficiency.
2Adaptability or versatility
If the preset read voltage is used on a storage device with voltage drift, then the original manufacturer's setting is maintained, but the error rate increases and data stability deteriorates
Solution Approach 1:
The patent implements dynamic voltage adaptation by adjusting read voltages based on actual device conditions rather than using fixed manufacturer settings. The system dynamically selects from multiple available voltages (e.g., 3.3V, 3.0V, 2.7V) depending on the specific storage device characteristics and observed performance. This dynamic approach allows the system to adapt to voltage drift and aging effects, maintaining data stability despite changes in device behavior over time.
3Measurement precision
If a linear regression model is used to search for optimal read voltage, then the accuracy of voltage selection is improved, but the calculation complexity increases
Solution Approach 1:
The patent changes the parameter representation from direct voltage values to a transformed space where linear regression is more effective. The system transforms voltage readings and error metrics into features suitable for linear modeling, allowing the use of simpler linear algorithms to achieve what would require complex non-linear optimization. This parameter transformation enables accurate optimal voltage selection while keeping computational requirements manageable through efficient matrix operations.
Data Source
AI summary
A method of searching for read voltages includes: respectively reading a memory segment through read voltages to obtain a sampling data, wherein the read voltages are composed of pairs of adjacent read voltages, and the memory segment is from a non-volatile flash memory; counting the number of first bits in each sampling data, wherein the numbers of first bits correspond to the read voltages respectively; obtaining number differences of the first bits corresponding to the pairs of adjacent read voltages; calculating a coefficient matrix according to the read voltages and the differences of the number of first bits; calculating fitting values according to the read voltages and the coefficient matrix, wherein the fitting value corresponds to the read voltage respectively; and selecting a read voltage corresponding to a minimum value among the fitting values to read the memory segment to perform an error correction program.