Memory Controller Read Voltage Adaptation
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Solution Overview
Problem
Conventional memory systems face challenges in accurately determining data due to variations in threshold voltage of memory cell transistors, leading to erroneous data determination and increased read latency, as they rely on a single determination voltage for read operations.
Innovation Solution
The memory system employs a controller that executes multiple read operations using different candidate determination voltages, ranks them based on threshold voltage variation, and applies error correction to determine the optimal voltage for reliable data retrieval, reducing read latency by learning and applying shift patterns that enhance error correction success.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single determination voltage is used for read operations, then the device complexity is low, but the reliability of data determination deteriorates due to threshold voltage variation
Solution Approach 1:
The system performs preliminary actions by pre-executing multiple read operations with different determination voltages before the actual data read request. These preliminary reads enable error correction and learning of optimal determination voltages in advance, so that when a real read request comes, the system can quickly apply the learned voltage without extensive trial-and-error, thus improving reliability while controlling complexity.
Solution Approach 2:
The system dynamically adjusts the determination voltage based on learned characteristics from preliminary read operations. Instead of using a fixed single voltage, the system adapts the determination voltage according to the specific data block being read and the error correction results, optimizing the balance between reliability and complexity for each read operation.
2Reliability
If multiple read operations are executed to correct errors, then the reliability of data determination improves, but the read latency increases
Solution Approach 1:
The system performs preliminary read operations and error correction in advance, before the actual data read request is fulfilled. By completing multiple trial reads and learning the optimal determination voltage during these preliminary operations, the system reduces the number of retries needed when a real read request arrives, thereby improving reliability without significantly increasing the perceived read latency for the user.
Solution Approach 2:
The system uses its own read operations to generate learning data for future reads. By automatically performing preliminary reads, analyzing error patterns, and updating determination voltage profiles for different data blocks, the system self-improves its performance over time without external intervention, reducing both latency and complexity in subsequent operations.
3Reliability
If determination voltage is changed for retrying read operations, then the reliability of data determination improves, but the read latency deteriorates
Solution Approach 1:
The system performs preliminary read operations with different determination voltages before the actual data read request. During these preliminary operations, the system learns which determination voltages work best for specific data blocks and stores this information. When a real read request comes, the system can directly apply the pre-learned optimal voltage, avoiding the need for time-consuming retries with voltage changes, thus improving reliability while minimizing latency.
Solution Approach 2:
The system changes the determination voltage parameter based on learned characteristics from preliminary operations. By maintaining profiles of optimal determination voltages for different data blocks and conditions, the system can quickly adjust the voltage parameter to the appropriate value without extensive trial-and-error during actual read operations, improving both reliability and latency performance.
Data Source
AI summary
A controller executes a plurality of first read operations and, when receiving a read request from a host, executes a second read operation. The first read operations are executed using, as determination voltage, different candidate values among a plurality of candidate values. In each of the first read operations, the controller executes error correction to acquired data, and acquires a first candidate value on the basis of results of the error corrections in the first read operations. The second read operation is executed using, as the determination voltage, a second candidate value that is ranked higher than the first candidate value.