Memory Controller Read-Level Correction Using History Voltage Data
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Solution Overview
Problem
Existing memory systems face challenges in determining an optimal read level when read operations fail, leading to inefficiencies and additional operations, particularly in volatile and nonvolatile memory devices.
Innovation Solution
A memory controller that includes a history voltage storage unit, read operation control unit, and read voltage setting unit to store and adjust read voltages based on historical average voltages, using Gaussian modeling and Gauss-Newton optimization to minimize additional read operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional read operations are performed without voltage adjustment, then the read operation is simple and fast, but the read operation fails when threshold voltage distributions vary
Solution Approach 1:
The patent applies dynamics by making the read voltage adjustable rather than fixed. The voltage setting unit dynamically selects from multiple candidate voltages based on threshold voltage distribution characteristics, allowing the system to adapt to varying memory cell conditions and improve read operation reliability.
Solution Approach 2:
The patent changes the voltage parameter by providing multiple candidate read voltages corresponding to different threshold voltage distributions. The system selects the appropriate voltage level based on the actual distribution characteristics, transforming a single parameter approach into a multi-parameter solution that handles variability.
2Measurement precision
If multiple read operations are performed to determine optimal read level, then the optimal read level can be determined, but additional read operations increase time consumption
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing multiple candidate read voltages and their corresponding threshold voltage distributions before actual read operations occur. This allows the system to quickly select the appropriate voltage without performing extensive trial read operations, reducing time consumption while maintaining precision.
Solution Approach 2:
The patent uses copying by creating a lookup table that stores pre-determined voltage-level distribution pairs. Instead of performing multiple read operations to determine optimal voltage levels, the system copies pre-computed results from the table, significantly reducing measurement time while maintaining accuracy.
3Reliability
If read voltage is adjusted based on threshold voltage distribution, then read operation reliability improves, but the control mechanism becomes more complex
Solution Approach 1:
The patent implements feedback by using the threshold voltage distribution information as feedback to the voltage setting unit. The distribution characteristics are fed back to select the appropriate read voltage, creating a closed-loop system that automatically adapts to varying memory conditions without requiring complex external control mechanisms.
Solution Approach 2:
The patent introduces an intermediary approach by using threshold voltage distribution statistics as a mediator between the raw read operation and the voltage selection. The distribution characteristics serve as an intermediate representation that simplifies the control logic, allowing reliable voltage selection without direct complex interaction with individual memory cells.
Data Source
AI summary
A memory controller includes a history voltage storage unit configured to store information on a plurality of history average voltages each representing an average voltages of each of a plurality of threshold voltage distributions for the plurality of memory cells, and a read voltage setting unit configured to, when a read operation performed by using a read voltage fails, determine a first cell count representing a number of cells measured based on the read voltage, determine a second cell count representing a number of cells predicted based on the read voltage through a first arithmetic operation performed based on an average voltage that is adjacent to the read voltage and selected from among the plurality of history average voltages, and adjust a level of the average voltage through a second arithmetic operation performed based on a difference between the first and second cell count.