Flash Memory Soft Data Readout from Leakage Current and Sensing Time
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Solution Overview
Problem
Conventional flash memory devices require multiple read voltages to determine the logical value of a memory cell, leading to increased latency and computational complexity in acquiring soft data, which is inefficient for both single-level and multi-level cell memory systems.
Innovation Solution
The method involves applying a single read voltage to a memory cell and measuring the sensing time and leakage current to assign a Log Likelihood Ratio (LLR) value, which is used as a soft input for error correction, thereby reducing the need for multiple read operations and simplifying the data acquisition process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple read voltages are applied to determine logical value of memory cell, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent changes the parameter being measured from binary conduction state to continuous side effect parameters (sensing time and leakage current magnitude). By measuring how long the bit line takes to discharge and the magnitude of leakage current during a single read voltage application, the system derives soft data that indicates both logical value and confidence level, eliminating the need for multiple read voltages while maintaining measurement precision
Solution Approach 2:
The patent introduces side effect measurements (sensing time and leakage current magnitude) as intermediary parameters that mediate between the single read voltage application and the final logical value determination. These intermediary measurements provide additional information about the memory cell state without requiring multiple direct read operations, thus reducing time loss while maintaining accuracy
2Reliability
If multiple read voltages are applied to determine logical value, then reliability of soft data is improved, but device complexity increases
Solution Approach 1:
The patent extracts soft data information from the side effects (sensing time and leakage current magnitude) that naturally occur during a single read operation, rather than requiring multiple read voltages and complex comparisons. By taking out and analyzing these inherent side effects, the system obtains reliable soft data with simpler computational processing
Solution Approach 2:
The patent utilizes the memory cell's own inherent characteristics (leakage current and discharge time) during the read operation to provide soft data information. The memory cell effectively serves itself by providing measurement data through its natural electrical behavior, eliminating the need for external complex measurement mechanisms
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces the latency and computational toll of reading memory cells by using a single read voltage and side effect measurements to determine logical values, improving the efficiency of data acquisition across various memory cell types.
Implementation Method 1
measuring a leakage current associated with sensing whether the bit line conducts with the read voltage applied
Implementation Method 2
measuring a time it takes to sense whether the bit line is conducting
Data Source
AI summary
Systems and methods for low latency acquisition of soft data from a memory cell based on a sensing time and/or a leakage current are described. In one embodiment, the systems and methods may include applying a first read voltage to a word line of a page of memory cells selected by a processor of a flash memory device for a read operation, applying a pass voltage to word lines associated with one or more different pages of memory cells of the memory block, upon applying the first read voltage sensing whether a bit line of a memory cell in the selected page conducts, measuring a side effect associated with sensing whether the bit line of the memory cell in the selected page conducts, and assigning a LLR value to the memory cell as a soft LDPC input based at least in part on the measured side effect.