Memory Device Overwrite Logic for Data Retention
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Solution Overview
Problem
Nonvolatile memory devices, such as flash memory, face challenges in maintaining high retention characteristics due to slow write and read speeds, which can lead to decreased threshold voltage distributions over time.
Innovation Solution
The proposed solution involves a memory device with control logic that performs an overwrite operation on selected memory blocks by increasing the threshold voltage of memory cells to a predetermined value based on the quantity of valid data stored, thereby improving retention characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flash memory is used to maintain data storage when power is cut off, then data retention is improved, but write and read speeds become slow
Solution Approach 1:
The system performs preliminary actions by identifying memory blocks with low valid data quantities before overwrite operations occur. The control logic proactively selects candidate memory blocks for overwrite based on valid data quantity thresholds, preparing the system to maintain retention characteristics before performance degradation occurs.
Solution Approach 2:
The invention changes operational parameters by dynamically adjusting overwrite selection criteria based on valid data quantity. Instead of uniform overwrite operations, the system modifies its behavior by selecting memory blocks for overwrite based on their valid data content, thereby optimizing the balance between retention maintenance and operational speed.
2Reliability
If overwrite operations are performed frequently to maintain threshold voltage distribution, then retention characteristics are improved, but device complexity and operational overhead increase
Solution Approach 1:
The control logic applies local quality by treating different memory blocks differently based on their individual valid data quantities. Instead of uniform overwrite operations across all blocks, the system selectively applies overwrite operations only to blocks with valid data quantities below the threshold, optimizing retention maintenance while reducing unnecessary operations.
Solution Approach 2:
The system uses copying mechanisms to manage memory block states, where control logic copies selection criteria and threshold values to determine overwrite candidates. This copying approach simplifies the control mechanism by using replicated threshold comparisons rather than complex real-time analysis of each memory block state.
3Reliability
If overwrite operations are performed on memory blocks with low valid data quantity, then retention characteristics are maintained, but loss of useful data occurs
Solution Approach 1:
The control logic implements feedback by continuously monitoring valid data quantities in memory blocks and adjusting overwrite selection based on this information. The system uses feedback from valid data quantity measurements to make informed decisions about which blocks require overwrite operations, preventing unnecessary overwrite of blocks with sufficient valid data.
Solution Approach 2:
The invention changes the operational parameter from uniform overwrite to threshold-based selective overwrite. By introducing the valid data quantity threshold as a changing parameter, the system dynamically determines overwrite eligibility, thereby preventing information loss while maintaining retention characteristics in blocks that need it.
Data Source
AI summary
The present technology relates to a memory device and a method of operating the same. The memory device includes a plurality of memory blocks each including a plurality of memory cells, peripheral circuits configured to perform a background operation and an overwrite operation on a selected memory block among the plurality of memory blocks, and control logic configured to control the peripheral circuits to perform the background operation and the overwrite operation, and the control logic controls the peripheral circuits to perform the overwrite operation including increasing a threshold voltage of the plurality of memory cells of the selected memory block to at least a predetermined threshold voltage value based on the quantity of valid data stored in the selected memory block.