NAND Memory Read-Voltage Tuning for Target Valley Detection
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Solution Overview
Problem
As the use time increases, charges stored in NAND memory cells vary due to repeated read operations and cross temperature, affecting the correctness of data reading.
Innovation Solution
A memory device and system that adjusts the read voltage to determine a target valley voltage by iteratively refining it based on a first result and threshold conditions, using mapping functions and correction coefficients to ensure accurate data reading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If read voltage is adjusted iteratively to determine target valley voltage, then data reading accuracy is improved, but device complexity and operation time increase
Solution Approach 1:
The patent segments the read voltage adjustment process into distinct stages: initial read voltage application, first result acquisition, threshold determination, voltage adjustment, and target valley voltage determination. Each stage processes specific parameters independently, reducing overall system complexity while maintaining accuracy.
Solution Approach 2:
The patent performs preliminary actions by pre-determining thresholds and adjustment parameters before the main read operation. The first threshold and correction coefficients are calculated in advance based on predicted valley voltages, allowing the actual read operation to proceed more efficiently with reduced real-time computation requirements.
2Measurement precision
If iterative voltage adjustment is performed to determine target valley voltage, then data reading accuracy is improved, but operation time increases
Solution Approach 1:
The patent implements feedback mechanisms where the first result from initial reads is used to determine the first threshold, which then guides the voltage adjustment process. This feedback loop allows the system to converge to the target valley voltage efficiently by continuously refining the read voltage based on previous measurement outcomes.
Solution Approach 2:
The patent changes key parameters during the process: read voltage is adjusted based on the difference between first result and first threshold, and correction coefficients are applied to refine the target valley voltage determination. These parameter changes enable adaptive optimization of read accuracy without requiring excessive iterative steps.
3Loss of time
If more processing is done in memory device rather than memory controller, then transmission time is reduced, but device complexity increases
Solution Approach 1:
The patent enables the memory device to perform self-service operations by determining its own target valley voltage using internal processing of read results and threshold comparisons. This self-determination capability eliminates the need for extensive communication with the memory controller, reducing transmission time while distributing computational workload to where the data resides.
Data Source
AI summary
Examples of the present application provide a memory device, a memory system, a memory controller, and an operation method. The memory device includes: an array of memory cells comprising multiple memory cells, wherein a preset number of memory cells form one codeword; and a peripheral circuit coupled with the array of memory cells and configured to: obtain a first result corresponding to at least one codeword at a target read voltage; obtain a first threshold according to the corresponding first result at the target read voltage; make at least one adjustment to the target read voltage, and after each adjustment, obtain a corresponding first result at the adjusted target read voltage; and determine a target valley voltage.