Continuous Sensing for Dynamic Read Point Determination in NAND Memory
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Solution Overview
Problem
Current memory devices face challenges in reading data quickly while maintaining accuracy, particularly in NAND memory systems, where variations in material age and variability lead to errors and increased software complexity.
Innovation Solution
A method is introduced that modifies the read process by varying the access line gate voltage over time, using continuous sensing to monitor total string current and apply signal processing to determine the optimal read point, allowing for dynamic feedback and common mode noise rejection without predetermined read levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional read schemes with predetermined read levels are used, then read time is reduced, but reading accuracy deteriorates due to material variability and age differences
Solution Approach 1:
The patent implements continuous sensing during the read operation to monitor the actual read levels in real-time. The system adjusts the read levels dynamically based on the sensed feedback, compensating for material variability and age-related changes. This feedback mechanism allows the system to maintain high reading accuracy while operating with faster read times compared to conventional schemes that rely on predetermined static read levels.
Solution Approach 2:
The patent transitions from static predetermined read levels to dynamic read levels that adapt during the read operation. By continuously sensing and adjusting read levels based on actual conditions, the system makes the read process dynamic rather than static, enabling it to respond to material variability and maintain accuracy across different device ages and conditions.
2Measurement precision
If compensation schemes such as cRLC and tempco adjustments are implemented, then reading accuracy is improved, but device complexity and software complexity increase
Solution Approach 1:
The patent implements a self-calibrating read system that automatically adjusts read levels through continuous sensing during normal read operations. The system performs its own calibration without requiring external intervention or complex software management, eliminating the need for separate cRLC and tempco adjustment mechanisms. This self-service approach maintains high reading accuracy while significantly reducing software complexity and firmware implementation time.
Solution Approach 2:
The patent merges the calibration function with the normal read operation by implementing continuous sensing during reads. Instead of having separate calibration and read processes, the system combines them into a unified operation where read levels are continuously adjusted during the read itself. This merging eliminates the need for multiple separate compensation schemes and reduces overall system complexity.
3Reliability
If continuous sensing is implemented to determine read points dynamically, then reading reliability is improved, but use of energy increases
Solution Approach 1:
The patent implements continuous sensing during the read operation, maintaining the sensing action throughout the entire read process rather than using discrete sampling. This continuous useful action ensures that read levels are constantly optimized, improving reading reliability. The energy consumption is managed by integrating the sensing function into the existing read operation infrastructure, minimizing additional energy overhead while maintaining continuous monitoring.
Data Source
AI summary
A variety of applications can include devices or methods that provide read processing of data in memory cells of a memory device without predetermined read levels for the memory cells identified. A read process is provided to vary a selected access line gate voltage over time, creating a time-variate sequence where memory cell turn-on correlates with programmed threshold voltage. Total string current of data lines of a group of strings of memory cells of the memory device can be monitored during a read operation of selected memory cells of the strings to which a ramp voltage with positive slope is applied to an access line coupled to the selected memory cells. Selected values of the change of the total current with respect to time, from the monitoring of the total current, are determined. Read points to capture data are based on the determined selected values. Additional devices, systems, and methods are discussed.