Memory Controller Dynamic Read Voltage Adjustment
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Solution Overview
Problem
The memory system faces challenges in accurately reading data due to changes in memory cell threshold voltage, leading to bit errors, which existing technologies struggle to address effectively.
Innovation Solution
The memory system employs a controller that performs a reference read operation, generates a histogram of memory cells across different threshold voltage bins, and uses estimation functions to determine actual read voltages, switching between first and second estimation functions based on stress conditions to optimize read operations and minimize bit errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the read voltage is adjusted to compensate for threshold voltage changes, then data reading accuracy is improved, but the system complexity increases due to multiple estimation functions and dynamic voltage adjustment mechanisms
Solution Approach 1:
The patent implements dynamic read voltage adjustment by selecting between first and second estimation functions based on stress conditions. The read voltage is not fixed but adapts in real-time according to the operational state of the memory device, allowing the system to maintain high reading accuracy under varying conditions without requiring a completely complex redesign of the memory architecture
Solution Approach 2:
The patent changes the parameter of read voltage based on stress conditions detected in the memory device. By monitoring stress levels and adjusting the read voltage accordingly (using different estimation functions for different stress conditions), the system optimizes data reading accuracy while managing complexity through parameter adaptation rather than structural complexity
2Reliability
If multiple estimation functions are used to handle different stress conditions, then reliability is improved, but the device complexity increases
Solution Approach 1:
The patent segments the estimation process by dividing it into at least two distinct estimation functions: a first estimation function for normal stress conditions and a second estimation function for high stress conditions. This segmentation allows each function to be optimized for its specific operational context, improving reliability without requiring a single overly complex estimation mechanism that would need to handle all possible conditions
Solution Approach 2:
The system dynamically selects between multiple estimation functions based on detected stress conditions. Rather than using a single static estimation function, the system adapts its estimation approach in real-time, switching between the first and second estimation functions as needed. This dynamic selection improves reliability across varying conditions while managing complexity through conditional logic rather than permanent structural complexity
3Reliability
If the read voltage is dynamically adjusted based on histogram and estimation functions, then bit error rate is reduced, but the operation time increases due to additional reference read operations
Solution Approach 1:
The patent performs reference read operations and histogram analysis in advance to determine the appropriate estimation function and read voltage before actual data reading. By preparing the voltage adjustment parameters beforehand based on preliminary measurements, the system reduces bit errors during actual data operations without requiring excessive time delays during critical read operations
Solution Approach 2:
The patent applies partial adjustment actions by selecting from multiple estimation functions rather than performing exhaustive searches for the optimal read voltage. The system performs reference reads and histogram analysis to a sufficient degree to identify the appropriate estimation function, then uses that function to determine the read voltage, balancing the need for accuracy with the need to limit operation time
Data Source
AI summary
A memory controller performs a reference read on a plurality of memory cells using reference read voltages, generates a histogram indicating the number of memory cells in different threshold voltage bins based on results of the reference read, estimates actual read voltages based on the histogram and a first estimation function, and reads data using the actual read voltages. When reading of the data with the actual read voltages estimated using the first estimation function fails, the memory controller estimates actual read voltages using a second estimation function different from the first estimation function and reads the data with the actual read voltages estimated using the second estimation function.