NAND Memory Partial Superblock Bad Block Threshold
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Solution Overview
Problem
Traditional superblocks in NAND memory devices are affected by bad blocks, leading to reduced performance and increased costs due to the need for redundant blocks or planes. Partial superblocks can mitigate this, but they result in decreased performance that may be perceptible to users.
Innovation Solution
The solution involves reallocating good blocks within a plane to replace bad blocks, forming partial superblocks with a quantity of bad blocks that satisfies a bad block threshold. This approach increases the number of partial superblocks, allowing their use while limiting performance decreases to non-perceptible levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional superblocks are used in NAND memory devices, then reliability is improved through redundant blocks, but device complexity and cost increase
Solution Approach 1:
The patent changes the parameter of superblock composition by allowing partial superblocks with a controlled number of bad blocks (threshold T), rather than requiring complete superblocks with zero bad blocks. This parameter change enables using previously discarded partial superblocks while maintaining reliability through the threshold-based acceptance criterion.
Solution Approach 2:
The patent treats bad blocks as acceptable imperfections that can be tolerated up to a certain threshold, rather than requiring perfect blocks. This approach uses less reliable but cheaper-to-manufacture memory blocks, reducing the need for extensive redundancy and lowering overall device complexity and cost.
2Ease of manufacture
If partial superblocks are used to mitigate bad block effects, then manufacturing yield is improved, but performance decreases to perceptible levels
Solution Approach 1:
The patent introduces a threshold parameter T that limits the number of bad blocks in a superblock. By controlling this parameter, the system accepts partial superblocks with some bad blocks (improving manufacturing yield) while ensuring the performance degradation remains below perceptible levels through the threshold constraint.
Solution Approach 2:
The patent implements a feedback mechanism where the number of bad blocks in each superblock is counted and compared against the threshold T. Superblocks exceeding the threshold are rejected or flagged, providing feedback control that ensures performance remains acceptable while maximizing the use of partially good blocks from manufacturing.
Data Source
AI summary
Methods, systems, and apparatuses related to source address memory management are described. For example, a controller can be coupled to a memory device to select a source block, a destination block, and a metadata block. The controller can store metadata indicative of an address of the source block in the metadata block. The controller can perform a memory management operation to transfer data from the source block to the destination block.