Memory Controller Read-Voltage Offset Recovery for NAND Errors
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Solution Overview
Problem
As the number of bits stored in each memory cell increases in nonvolatile memory devices, the probability of data errors also increases, necessitating effective read operations that can recover original data even when errors occur.
Innovation Solution
A storage device with a memory controller that performs multiple read operations using different voltage levels and adjusts offsets based on the data received, followed by a soft decision process to correct errors and ensure data integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of bits stored in each memory cell increases, then the storage capacity increases, but the probability of data errors increases
Solution Approach 1:
The patent segments the read operation into multiple stages: initial read, offset adjustment phase, and refined read phase. By dividing the read process into discrete steps with intermediate analysis, the system can detect and correct errors that would otherwise go unnoticed in high-density storage, thereby maintaining data reliability despite increased storage capacity
Solution Approach 2:
The patent implements a feedback mechanism where the results of the initial read operation are analyzed to dynamically adjust the read voltage offset. This closed-loop feedback allows the system to compensate for voltage drift and errors automatically, ensuring high data reliability even as storage density increases
2Reliability
If multiple read operations with different voltage levels are performed, then data reliability improves, but the read operation time increases
Solution Approach 1:
The patent performs a preliminary read operation to establish baseline data and determine the need for offset adjustment. This preliminary action allows the system to skip the time-consuming offset adjustment and second read operations when not necessary, thereby reducing average read time while maintaining the capability to recover data when errors occur
Solution Approach 2:
The patent dynamically adapts the read operation sequence based on the results of each step. If the initial read succeeds without errors, the process terminates early. If errors are detected, the system dynamically transitions to offset adjustment and subsequent read operations. This dynamic approach optimizes read time by avoiding unnecessary operations while ensuring data reliability when needed
Data Source
AI summary
A storage device includes a nonvolatile memory device and a memory controller. The memory controller receives first data from the nonvolatile memory device based on a first read command, and performs error correction on the first data. When the error correction fails, the memory controller transmits a second read command and second read voltage information to the nonvolatile memory device, receives second data from the nonvolatile memory device, transmits a third read command and third read voltage information to the nonvolatile memory device, and receives third data from the nonvolatile memory device. The memory controller adjusts an offset based on the second data and the third data, transmits a fourth read command, fourth read voltage information, and the offset to the nonvolatile memory device, receives fourth data from the nonvolatile memory device, and performs a soft decision process based on the fourth data.