Adaptive NVM Read Windows for Uncorrectable Bit Errors
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Solution Overview
Problem
Non-volatile memory (NVM) systems experience performance degradation over time, leading to increased bit errors that existing error correction codes (ECC) cannot correct, limiting their reliability and useful life.
Innovation Solution
The implementation of adaptive error correction methods that dynamically adjust sense amplifier read detection windows by varying operating parameters such as reference currents and voltages to correct bit errors that were previously uncorrectable, allowing for the identification and correction of double-bit errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard ECC routines are used to correct bit errors, then single-bit errors can be corrected, but double-bit errors cannot be corrected
Solution Approach 1:
The patent applies dynamics by making the read detection window adjustable rather than fixed. The sense amplifier's read detection window is dynamically varied based on the detected error type, allowing the system to adapt between correcting single-bit errors and attempting to correct double-bit errors by shifting the detection window to different voltage thresholds.
Solution Approach 2:
The patent changes the operating parameter of the sense amplifier (read detection window voltage threshold) based on the error condition detected by the ECC routine. When a double-bit error is detected, the system adjusts the read detection window parameter to a different voltage level to potentially recover the correct data, thereby extending error correction capability beyond standard single-bit correction.
2Productivity
If NVM systems are used over time, then more data can be stored and accessed, but performance degradation increases bit errors
Solution Approach 1:
The patent implements feedback by using the ECC routine's error detection output to control the read detection window adjustment. The system continuously monitors for errors during read operations and dynamically adjusts the detection parameters based on this feedback, creating a closed-loop system that adapts to aging-induced performance degradation.
Solution Approach 2:
The patent applies preliminary action by adjusting the read detection window before final data validation occurs. When an error is detected, the system proactively attempts to re-read the data with adjusted detection parameters before declaring a read failure, thereby preemptively correcting errors that would otherwise propagate.
3Reliability
If read detection windows are fixed, then sense amplifier operation is simple, but uncorrectable bit errors increase with NVM aging
Solution Approach 1:
The patent transforms the static read detection window into a dynamic parameter that can be adjusted based on detected error conditions. This allows the sense amplifier to adapt its detection characteristics to match the degraded NVM cell performance, improving reliability without requiring a complete redesign of the sense amplifier architecture.
Data Source
AI summary
Adaptive error correction for non-volatile memories is disclosed that dynamically adjusts sense amplifier read detection windows. Memory control circuitry uses error correction code (ECC) routines to detect bit errors that are non-correctable using these ECC routines. The memory control circuitry then dynamically adjusts sense amplifier read detection windows to allow for correct data to be determined. Corrected data can then be output to external circuitry. The corrected data can also be stored for later access when subsequent read operations attempt to access address locations that previously suffered bit failures. The adaptive error correction can also be used with respect to memories that are not non-volatile memories.