Memory Controller Optimal Read Voltage Determination
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Solution Overview
Problem
Current storage devices face challenges in achieving optimal data recovery rates due to variations in threshold voltages of memory cells, leading to failed read operations when using default read voltages.
Innovation Solution
A memory controller and method that determine an optimal read voltage by calculating the average threshold voltage and cell number information from adjacent threshold voltage distributions, using a formula that incorporates variance and cell distribution ratios to minimize read operation failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a default read voltage is used for reading memory cells, then the read operation can be performed with simple control logic, but the data recovery rate deteriorates due to threshold voltage variations
Solution Approach 1:
The patent dynamically changes the read voltage parameter based on the detected threshold voltage distribution characteristics. The memory controller adjusts the read voltage to optimally separate adjacent threshold voltage distributions, thereby improving data recovery rate while maintaining reasonable control complexity through automated adaptation.
Solution Approach 2:
The patent implements a feedback mechanism where the memory controller detects threshold voltage distributions, calculates optimal read voltages based on distribution parameters (average threshold voltages and cell numbers), and adjusts subsequent read operations accordingly. This closed-loop feedback enables the system to adapt to varying memory cell conditions and maintain high data recovery rates.
2Reliability
If the read voltage is adjusted to account for threshold voltage variations, then the data recovery rate improves, but the control logic complexity increases
Solution Approach 1:
The memory controller performs self-diagnosis and self-adjustment by detecting threshold voltage distributions and automatically calculating optimal read voltages without external intervention. This self-service capability improves data recovery while avoiding the need for complex external control systems or manual calibration procedures.
Solution Approach 2:
The patent performs preliminary detection of threshold voltage distributions and calculation of optimal read voltages before actual data read operations. This preliminary action prepares the system in advance, allowing the main read operations to proceed with optimized parameters without real-time complexity during critical data retrieval.
3Measurement precision
If multiple reference voltages are used to detect threshold voltage distributions, then the accuracy of optimal read voltage determination improves, but the read operation time increases
Solution Approach 1:
The patent uses multiple reference voltages to detect threshold voltage distributions only when necessary (e.g., when data recovery rate deteriorates or initially), rather than continuously for every read operation. This partial application of the complex measurement process achieves high accuracy when needed while minimizing overall time loss through selective execution.
Data Source
AI summary
A storage device configured to provide an improved data recovery rate includes a memory device including a plurality of memory cells and a memory controller. The memory controller includes a read operation controller for controlling the memory device to perform a read operation by applying a default read voltage or optimal read voltage to a selected word line coupled to selected memory cells among the plurality of memory cells; and an optimal read voltage operating component for determining the optimal read voltage when the read operation using the default read voltage fails, based on an average threshold voltage and cell number information which are information on a memory cell number for each of first and second distributions which are adjacent threshold voltage distributions among threshold voltage distributions that the threshold voltages of the selected memory cells form.