Read Voltage Detection in Memory Sub-Systems
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Solution Overview
Problem
Conventional memory systems face inefficiencies in detecting and correcting errors due to shifts in optimized read voltage for memory cells, leading to prolonged latency and inefficient retry processes when errors exceed threshold levels.
Innovation Solution
A memory sub-system that computes an optimized read voltage based on signal and noise characteristics of memory cells, determining whether it is within a correct voltage range, and adjusts test voltage ranges as needed to accurately read memory cells, thereby improving data retrieval efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fixed read voltage is used for memory cells, then device complexity is reduced, but measurement precision deteriorates due to voltage shifts causing read errors
Solution Approach 1:
The memory device performs self-detection and self-adjustment of read voltage using built-in calibration circuits. The device measures its own signal and noise characteristics and automatically computes the optimized read voltage without requiring external intervention, enabling the system to serve itself in maintaining voltage accuracy
Solution Approach 2:
The system implements a feedback mechanism where read voltage is continuously monitored based on signal and noise characteristics, and adjustments are made according to the detected voltage accuracy. The calibration process uses feedback from measured characteristics to dynamically adjust the read voltage to optimal levels
Solution Approach 3:
The patent changes the read voltage parameter dynamically based on detected signal and noise characteristics. Instead of using a fixed voltage, the system adjusts the voltage parameter in response to changing conditions, computing optimized voltage values that adapt to the current state of the memory cells
2Measurement precision
If read voltage calibration is performed frequently, then data retrieval accuracy is improved, but loss of time increases due to calibration overhead
Solution Approach 1:
The system performs preliminary calibration actions by pre-computing and storing optimized read voltage values based on signal and noise characteristics before actual data retrieval operations. This preliminary preparation reduces the time needed during actual read operations
Solution Approach 2:
The patent applies partial calibration by performing voltage optimization only when necessary based on detected voltage accuracy levels. Instead of continuous full calibration, the system selectively applies calibration actions only when voltage drift exceeds thresholds, reducing overall calibration time while maintaining accuracy
3Adaptability or versatility
If voltage range is expanded to cover all possible optimized read voltages, then adaptability is improved, but device complexity increases due to wider test voltage requirements
Solution Approach 1:
The patent segments the voltage range into multiple discrete test voltage levels rather than using a continuous wide range. By dividing the voltage spectrum into specific segments or steps, the system achieves comprehensive coverage while reducing the complexity of generating and managing test voltages
Solution Approach 2:
The system applies local quality by using different test voltage strategies for different regions of the voltage range. Instead of uniformly testing all voltages, the system focuses test efforts on locally relevant voltage regions based on detected signal and noise characteristics, reducing overall test complexity while maintaining adaptability
Data Source
AI summary
A memory device to program a group of memory cells to store multiple bits per memory cell. Each bit per memory cell in the group from a page. After determining a plurality of read voltages of the group of memory cells, the memory device can read the multiple pages of the group using the plurality of read voltages. For each respective page in the multiple pages, the memory device can determine a count of first memory cells in the respective page that have threshold voltages higher than a highest read voltage, among the plurality of read voltages, used to read the respective page. The count of the first memory cells can be compared with a predetermined range of a fraction of memory cells in the respective page to evaluate the plurality of read voltages (e.g., whether any of the read voltages is in a wrong voltage range).