Flash Memory Read Reference Voltage Determination
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Solution Overview
Problem
Solid state drives (SSDs) using NAND flash memory face errors in data reading due to deviations in reference voltage from factory settings caused by read, write, and retention operations over time.
Innovation Solution
A method and apparatus that determine a reference voltage by reading data from flash memory pages using multiple reference voltages, adjusting these voltages to minimize erroneous bits, and selecting the voltage with the smallest number of errors, allowing for accurate data reading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If factory setting reference voltage is used for reading data, then the reading operation can be performed with simple initial configuration, but data reading errors occur due to voltage deviation over time
Solution Approach 1:
The patent applies preliminary action by performing reference voltage detection and determination before actual data reading operations. The system pre-detects the current reference voltage level and determines the appropriate read reference voltage based on detected error patterns, so that when data reading is needed, the correct voltage is already established, preventing reading errors without complicating the user operation
Solution Approach 2:
The patent implements feedback by continuously monitoring reading errors and using this information to adjust the reference voltage. The system detects errors in read data, feeds this error information back to the voltage control mechanism, and adjusts the reference voltage accordingly to minimize future errors, creating a closed-loop system that maintains reading accuracy over time
2Measurement precision
If multiple reference voltages are tested to find the optimal one, then data reading accuracy is improved, but the detection and measurement process becomes more complex
Solution Approach 1:
The patent applies partial action by testing multiple reference voltages systematically rather than exhaustively checking all possible values. The system tests a predetermined set of candidate voltages and selects the best one from this limited set, achieving sufficiently high precision without the complexity of exhaustive search or continuous optimization
Solution Approach 2:
The patent utilizes parameter changes by systematically varying the reference voltage parameter across multiple test values. The system changes the voltage parameter to different predetermined levels, measures the error rate at each level, and identifies the optimal parameter setting, transforming a complex continuous optimization problem into a manageable discrete parameter selection
3Reliability
If reference voltage is adjusted frequently to maintain accuracy, then data reading reliability is improved, but the operation time and processing duration increase
Solution Approach 1:
The patent implements periodic action by adjusting the reference voltage at predetermined intervals or under specific conditions rather than continuously or too frequently. The system performs voltage detection and adjustment periodically based on operational milestones or error thresholds, maintaining reading reliability while minimizing the time spent on voltage adjustments
Solution Approach 2:
The patent applies universality by designing a reference voltage determination mechanism that serves multiple functions: it detects voltage drift, determines optimal read voltage, validates data integrity, and guides subsequent reading operations. This multi-functional approach consolidates what could be multiple separate operations into a single integrated process, reducing overall processing time
Data Source
AI summary
A method and apparatus for determining a reference voltage id disclosed. The method may include: reading data from a first flash memory page by using different reference voltages, and taking, as a first target reference voltage, one of the different reference voltages at which the first number of erroneous bits of the data that is read reaches a converegence value. The first flash memory page is any one of multiple flash memory pages of a flash memory block to be tested. The method may include adjusting the first target reference voltage to obtain second target reference voltages; and reading data from the flash memory pages by using the second target referece voltages, and taking, as a target reference voltage, one of the second target reference voltages at which the second number of erroneous bits of the data that is read is the smallest.