Flash Memory Read Level Control Using ECC Error Feedback
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Solution Overview
Problem
Conventional flash memory read levels are fixed, leading to increased errors when threshold voltage distributions change, as they fail to adapt to variations in data storage, resulting in suboptimal read levels and errors.
Innovation Solution
A read level control apparatus and method that includes an error control code (ECC) decoding unit, a monitoring unit to track bit error rate (BER), an error determination unit to assess error rates, and a level control unit to dynamically adjust the read level based on error rates, thereby reducing errors by adjusting the reference voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed read levels are used in flash memory, then device complexity is reduced and ease of operation is improved, but data accuracy and reliability deteriorate when threshold voltage distributions change
Solution Approach 1:
The patent implements a feedback mechanism where the monitoring unit continuously monitors bit error rates from ECC decoded data, and the level control unit adjusts read levels based on this feedback. This closed-loop system automatically adapts to threshold voltage distribution changes, improving data accuracy without requiring complex manual intervention or system redesign
Solution Approach 2:
The read level control system performs self-adjustment through the monitoring unit and level control unit that automatically detect error rates and modify read levels without external intervention. The system serves itself by using its own error information to optimize its performance, eliminating the need for complex external calibration procedures
2Reliability
If dynamic read level adjustment is implemented, then data accuracy and reliability improve, but device complexity and measurement precision requirements increase
Solution Approach 1:
The patent introduces an ECC decoding unit as an intermediary that processes read data and provides error information to the monitoring unit. This intermediary component simplifies the measurement process by converting raw read data into actionable error rate metrics that the level control unit can use for adjustment, reducing the complexity of direct error measurement
3Adaptability or versatility
If read levels are fixed, then ease of manufacture and device simplicity are maintained, but adaptability to threshold voltage changes deteriorates
Solution Approach 1:
The patent transforms the static fixed read level system into a dynamic system where read levels can automatically adjust based on monitored error rates. The level control unit enables continuous adaptation to threshold voltage distribution changes caused by floating poly couplings or charge losses, making the system flexible and responsive to environmental variations
Solution Approach 2:
The monitoring unit provides continuous feedback on bit error rates to the level control unit, creating a self-regulating system that adapts to threshold voltage changes. This feedback mechanism enables the system to automatically compensate for variations in floating gate flash memory characteristics without requiring complex manual recalibration
Data Source
AI summary
Various read level control apparatuses and methods are provided. In various embodiments, the read level control apparatuses may include an error control code (ECC) decoding unit for ECC decoding data read from a storage unit, and a monitoring unit for monitoring a bit error rate (BER) based on the ECC decoded data and the read data. The apparatus may additionally include an error determination unit for determining an error rate of the read data based on the monitored BER, and a level control unit for controlling a read level of the storage unit based on the error rate.