Dynamic Read Voltage Adjustment for Flash Memory Error Correction
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Solution Overview
Problem
Non-volatile data storage devices face increased bit error rates due to shifting threshold voltages in flash memory cells, leading to inaccurate data reading and higher ECC decoding latency, which affects storage density and throughput.
Innovation Solution
The system updates read voltages based on error type counts, adjusting them dynamically during ECC decoding to reduce errors and improve decoding efficiency without requiring separate calibration operations, thereby enhancing data accuracy and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple bits are stored per flash memory cell to increase storage density, then storage density is improved, but bit error rate increases
Solution Approach 1:
The patent dynamically adjusts read voltage parameters based on detected error patterns. By monitoring error types (e.g., read 0 when 1 was programmed vs. read 1 when 0 was programmed) and updating read voltages accordingly, the system adapts to threshold voltage shifts caused by storing multiple bits per cell, thereby maintaining reliability while preserving high storage density
2Measurement precision
If separate calibration operations are performed to determine read thresholds, then reading accuracy is improved, but read throughput decreases
Solution Approach 1:
The patent merges the calibration function with regular read operations. Error type counting and read voltage updates are performed during normal data reading using existing ECC decoding logic, eliminating the need for separate calibration operations. This integration maintains reading accuracy through continuous voltage adaptation while preserving maximum read throughput
Solution Approach 2:
The system performs self-calibration by automatically detecting error patterns during read operations and adjusting its own read voltages without external intervention. The ECC decoder identifies error types and triggers voltage updates autonomously, enabling the system to maintain optimal reading accuracy while continuously processing data without dedicated calibration overhead
3Reliability
If high resolution reading is used to enhance ECC correction capability, then error correction is improved, but read time increases
Solution Approach 1:
The patent implements dynamic read voltage adjustment that adapts to changing error conditions. By continuously monitoring error types and updating read voltages in real-time, the system optimizes the separation between threshold voltage distributions, enabling standard resolution reading to achieve sufficient error correction capability without resorting to time-consuming high resolution reading operations
Data Source
AI summary
A method includes, in a data storage device that includes a non-volatile memory, reading data from the non-volatile memory using a first read voltage. The method includes determining a first count of errors in the data having a first error type and a second count of errors in the data having a second error type. A value of the first read voltage is selectively updated based on a comparison of the first count to the second count.