Memory Controller Read Voltage Optimization
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Solution Overview
Problem
Existing memory controllers face challenges in performing read operations with high reliability when the threshold voltage distribution of memory cells is degraded, leading to potential read errors.
Innovation Solution
A method is introduced where a memory controller sets an optimum read voltage by applying a test read voltage to a selected word line, receiving cell count information, and renewing the test read voltage using a cost function determined for each read voltage level, iteratively adjusting until an optimum voltage is found to ensure reliable read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed read voltage is used for read operations, then the device complexity is reduced, but the reliability deteriorates when threshold voltage distribution is degraded
Solution Approach 1:
The patent implements dynamic read voltage adjustment by iteratively renewing the read voltage based on cell count information and cost function calculations. The memory controller adapts the read voltage to match the actual threshold voltage distribution of memory cells, transforming a static voltage approach into a dynamic one that responds to degradation conditions.
Solution Approach 2:
The patent employs feedback mechanisms where cell count information from test read operations is used to calculate cost functions, which then guide the renewal of read voltage. This closed-loop feedback system continuously optimizes the read voltage to maintain high reliability even as threshold voltage distribution degrades over time.
2Reliability
If the threshold voltage distribution is degraded, then the manufacturing precision is reduced, but the reliability can be maintained through iterative voltage adjustment
Solution Approach 1:
The patent changes the read voltage parameter dynamically based on observed threshold voltage distribution characteristics. By calculating cost functions from cell count information and using these to renew the read voltage, the system adapts to manufacturing variations and degradation without requiring precise control of the threshold voltage distribution itself.
3Reliability
If an iterative voltage renewal process is performed, then the reliability is improved, but the productivity is reduced due to additional operations
Solution Approach 1:
The patent performs preliminary test read operations and cost function calculations to determine the optimal read voltage before actual data read operations. This preliminary action ensures that when production reads are performed, they use the already-optimized voltage, minimizing the impact of iterative processes on overall productivity.
Data Source
AI summary
A method of setting a read voltage by a memory controller and a storage device are provided. The method includes controlling a memory device to read data from memory cells by applying a test read voltage to a selected word line; receiving, from the memory device, cell count information corresponding to a read operation of the memory device, and renewing the test read voltage by using the cell count information and a cost function to find an optimum read voltage, the cost function being determined for each read voltage level; and determining a read voltage by performing the controlling of the memory device and the renewing of the test read voltage at least once.