Memory Cell Threshold Distribution Using Coarse Read Estimates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Memory systems face high latency and reduced processing bandwidth when determining voltage threshold distributions across memory cells, particularly in NAND systems, due to the need for adjusting read trims for each operation.
Innovation Solution
Implementing a coarse threshold estimate (CTE) read method to identify memory cell types and voltage ranges, setting reference voltages, and incrementing them until they reach the endpoints of these ranges to determine voltage threshold distributions with reduced latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If read trim is adjusted for each read operation to determine voltage threshold distribution, then measurement precision is improved, but latency increases and processing bandwidth decreases
Solution Approach 1:
The patent performs preliminary characterization of memory cells by conducting multiple read operations with different read trims to establish voltage threshold distributions. This preliminary action is performed once during manufacturing or initialization, allowing the memory system to store the characterized data and avoid repeated time-consuming measurements during normal operation. The preliminary characterization enables fast lookup during subsequent read operations.
Solution Approach 2:
The patent creates a copy of the voltage threshold distribution characteristics for each memory cell type and stores this information in a lookup table or database. Instead of performing real-time measurements, the system retrieves pre-computed distribution data from the copy, significantly reducing latency while maintaining measurement precision for error correction purposes.
2Measurement precision
If read trim is adjusted for each read operation to determine voltage threshold distribution, then measurement precision is improved, but processing bandwidth is reduced
Solution Approach 1:
The patent performs preliminary characterization of memory cells by conducting multiple read operations with different read trims to establish voltage threshold distributions. This preliminary action is performed once during manufacturing or initialization, allowing the memory system to store the characterized data and avoid repeated time-consuming measurements during normal operation. The preliminary characterization enables fast lookup during subsequent read operations.
Solution Approach 2:
The patent creates a copy of the voltage threshold distribution characteristics for each memory cell type and stores this information in a lookup table or database. Instead of performing real-time measurements, the system retrieves pre-computed distribution data from the copy, significantly reducing latency while maintaining measurement precision for error correction purposes.
3Measurement precision
If multiple read operations with different read trims are performed to determine voltage threshold distribution, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent segments the memory cell population into different types based on their voltage threshold characteristics (e.g., SLC, MLC, TLC, QLC). Each segment is characterized separately and stored with its specific voltage threshold distribution parameters. This segmentation allows the system to simplify read operations by selecting the appropriate pre-characterized profile based on memory cell type, reducing overall system complexity.
Solution Approach 2:
The patent performs preliminary characterization of memory cells by conducting multiple read operations with different read trims to establish voltage threshold distributions. This preliminary action is performed once during manufacturing or initialization, allowing the memory system to store the characterized data and avoid repeated time-consuming measurements during normal operation. The preliminary characterization enables fast lookup during subsequent read operations.
Data Source
AI summary
Methods, systems, and devices for voltage threshold distribution using read estimate are described. A memory system may determine a voltage threshold distribution of memory cells. For a target memory cell, the memory system may identify the type of memory cell and identify voltage ranges associated with the memory cell based on the type. The memory system may set reference voltages for each voltage range, and read the memory cell using the reference voltages by counting the quantity of logic states between the reference voltages and endpoints of the voltage ranges. The memory system may increment the reference voltages and reread the memory cell using the incremented reference voltages. After incrementing the reference, the memory system may use the counts determined during the reading operations to determine the voltage threshold distribution.