Memory Controller SPO Recovery Using Predetermined Read Voltage
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Solution Overview
Problem
Existing memory systems face significant challenges in reducing the time required for recovery operations after a sudden power off (SPO), as the process of searching for valid word lines to recover data is time-consuming due to the need to apply multiple read voltages and perform error correction decoding.
Innovation Solution
A controller and operating method that utilize a predetermined read voltage to search for a valid word line in reverse program order, allowing for efficient identification and recovery of data by writing valid data from the affected memory block to another open block, thereby reducing the recovery time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple read voltages are applied to search for valid word lines, then measurement precision is improved, but time required for recovery operation increases
Solution Approach 1:
The patent applies preliminary action by performing a preliminary search for valid word lines using a first read voltage before the main recovery operation. This preliminary search identifies candidate word lines that are likely to contain valid data, thereby reducing the scope of subsequent operations and overall recovery time while maintaining identification accuracy.
Solution Approach 2:
The recovery operation is segmented into multiple phases: first searching for valid word lines using a first read voltage, then performing error correction decoding only on identified valid word lines using a second read voltage. This segmentation avoids applying multiple read voltages to all word lines, significantly reducing total operation time while preserving measurement precision for actual data recovery.
2Reliability
If error correction decoding is performed during recovery, then data reliability is improved, but recovery operation time increases
Solution Approach 1:
The patent segments the recovery process into two distinct stages: first identifying valid word lines using a read voltage search, then performing error correction decoding only on those identified valid word lines. This segmentation ensures that time-consuming error correction operations are applied only where necessary, maintaining data reliability while minimizing overall recovery time.
Solution Approach 2:
Instead of performing error correction decoding on all word lines (excessive action), the patent applies error correction decoding only to word lines that have been identified as valid through preliminary searching. This partial action approach maintains data reliability for actually recovered data while avoiding wasteful time expenditure on invalid word lines.
3Loss of information
If data is recovered from all word lines, then data completeness is improved, but recovery operation complexity increases
Solution Approach 1:
The patent uses preliminary action by first searching for valid word lines using a read voltage before initiating the full data recovery process. This preliminary identification step ensures that subsequent recovery operations focus only on word lines containing valid data, maintaining data completeness while significantly reducing operational complexity compared to processing all word lines uniformly.
Data Source
AI summary
An operating method of a controller includes: searching, by using a predetermined read voltage, a valid word line coupled to a memory cell having a predetermined program status, among word lines coupled to a first open memory block of a memory device when a memory system is powered on after a sudden power off (SPO); and reading data from the memory cell coupled to the valid word line, and writing the read data into a second open memory block.