Memory Controller Feedback for Soft Read Voltage Offset Compression
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Solution Overview
Problem
Existing memory systems face challenges in effectively correcting errors in non-volatile memory devices due to deteriorated threshold voltage distributions, leading to high probabilities of uncorrectable errors in hard decision data, especially in triple-level cell (TLC) memory devices.
Innovation Solution
The system employs a memory controller that receives compressed soft decision data from a memory device, counts the number of specific bit positions, and requests a change in voltage offset to improve data reliability, enabling error correction through log-likelihood ratio calculations and low-density parity check methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If soft decision data is compressed to reduce data transmission volume, then data transmission efficiency is improved, but data loss during compression increases
Solution Approach 1:
The memory controller counts the number of position values in compressed soft decision data and uses this count as feedback to determine whether to request a voltage offset change. When the position value count exceeds a threshold, indicating potential data loss, the system requests a voltage offset change to improve compression quality and reduce data loss.
Solution Approach 2:
The system changes the voltage offset parameter used during soft decision data compression. By adjusting the voltage offset, the memory device can generate soft decision data with different characteristics that compress more effectively, reducing position value counts and minimizing data loss while maintaining transmission efficiency.
2Speed
If hard decision reading is used for fast data retrieval, then reading speed is improved, but error rate increases due to deteriorated threshold voltage distributions
Solution Approach 1:
The patent introduces soft decision data as an intermediary between hard decision reading and error correction. The soft decision data, generated using voltage offsets, provides reliability information that helps the error correction circuit distinguish between threshold voltage regions, thereby reducing uncorrectable errors while maintaining fast reading speeds.
Solution Approach 2:
The system performs preliminary soft decision reading with voltage offsets before final error correction. This preliminary action generates compressed soft decision data that contains reliability information, allowing the error correction circuit to more effectively correct errors in the hard decision data without sacrificing reading speed.
Data Source
AI summary
An example memory system includes a memory device and a memory controller. The memory device is configured to read, from a memory cell array, hard decision data based on a hard read voltage and first soft decision data based on first soft read voltages obtained based on the hard read voltage and a first voltage offset, generate a first compressed sub-segment based on encoding a position of a bit having a first value into a position value for each of first soft decision sub-segments in the first soft decision data, and output first compressed data including first compressed sub-segments. The memory controller is configured to receive the first compressed data, count the number of position values in each of the first compressed sub-segments, and provide, to the memory device based on the counted number, a command to request a change of a voltage offset and a recompression operation.