Flash Memory Read Sequencing Against Power Drop Failures
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Solution Overview
Problem
Existing memory cell reading methods in flash memory devices face issues with power noise and power drop leading to failed readings of memory cells after an initial successful read.
Innovation Solution
A memory storage device and reading method that simultaneously reads signature and option memory cells, ensuring correct reading by determining the success of signature memory cell reads before considering option memory cells, and optionally maintaining word line signals in an enabled state for continuous power supply during multiple readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If memory cells are read sequentially one after another, then the first memory cell can be read successfully, but subsequent memory cells fail to read due to power noise and power drop
Solution Approach 1:
The patent merges the reading operations of signature memory cells and option memory cells into a single simultaneous operation. By applying the word line signal to both cell types at the same time and using a unified reading process, the patent eliminates the sequential reading approach that causes power noise accumulation. This combining strategy ensures that all memory cells on a word line are read before the word line signal is deactivated, thereby preventing power drop from affecting subsequent reads.
Solution Approach 2:
The patent performs preliminary verification by reading signature memory cells first (which are specifically designed for this purpose) to detect potential power noise or power drop issues before reading the option memory cells. This preliminary action allows the system to identify and handle reading failures early in the process, preventing the propagation of errors to subsequent memory cell readings and improving overall reading reliability.
2Reliability
If signature memory cells and option memory cells are read simultaneously, then reading reliability is improved, but device complexity increases due to additional signature memory cells
Solution Approach 1:
The patent segments the memory cell array into two distinct functional parts: signature memory cells and option memory cells. This segmentation allows each type to serve its specific purpose - signature cells for verification and power noise detection, and option cells for actual data storage. By dividing the memory structure this way, the patent achieves reliable simultaneous reading while maintaining clear functional separation, making the increased complexity manageable and purposeful rather than arbitrary.
Solution Approach 2:
The signature memory cells serve multiple functions: they act as regular data storage cells, serve as verification cells for detecting power noise and power drop, and function as indicators for reading status. This multi-functionality reduces the need for separate dedicated verification structures, thereby limiting the increase in device complexity while achieving improved reading reliability through the simultaneous reading mechanism.
Data Source
AI summary
A memory storage device including a memory cell array and a controller circuit is provided. The memory cell array includes signature memory cells and option memory cells. The controller circuit is coupled to the memory cell array. The controller circuit is configured to read the signature memory cells and the option memory cells at the same time. When the reading of the signature memory cells passes, the controller circuit determines that the reading of the option memory cells passes.