Flash Memory Read Voltage Adjustment for Charge Loss Mitigation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Flash memory devices experience charge loss due to thermal stress and extended use, leading to shifting and widening of threshold voltage distributions, which can result in read errors and render the memory unusable.
Innovation Solution
Implementing methods such as using single-level cells (SLC) or multiple-level cells (MLC) with padding techniques, programming multiple copies of data and its complements, and adjusting read voltage levels based on the number of memory cells in a particular data state to mitigate charge loss failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If flash memory cells are used for extended use or subjected to thermal stress, then the memory can operate for longer periods, but charge loss occurs causing threshold voltage distributions to shift and widen leading to read errors
Solution Approach 1:
The patent performs preliminary detection of charge loss by reading memory cells before actual read operations. By detecting threshold voltage shifts early and identifying cells that have lost charge, the system can take preventive actions such as re-programming affected cells or adjusting read thresholds, thereby preventing read errors before they occur during normal operation.
Solution Approach 2:
The patent implements a feedback mechanism where the results of preliminary read operations are used to adjust subsequent read operations. By monitoring the distribution of read values and detecting deviations from expected thresholds, the system dynamically adjusts read thresholds and identifies cells requiring re-programming, creating a closed-loop system that continuously compensates for charge loss.
2Quantity of substance
If multiple-level cells (MLC) are used to increase storage capacity, then memory density improves, but charge loss has greater impact on data integrity compared to single-level cells
Solution Approach 1:
The patent applies copying by storing multiple copies of data in different memory cells. When charge loss affects one cell, the system can retrieve the original data from another copy and use it to re-program the affected cell, thereby restoring data integrity without requiring external intervention.
Solution Approach 2:
The patent changes operational parameters by adjusting read thresholds based on detected charge loss patterns. For MLC cells, the system dynamically modifies the voltage thresholds used to distinguish between different data states, compensating for threshold voltage shifts caused by charge loss and maintaining accurate data retrieval.
3Ease of operation
If pre-programmed data is stored in memory prior to connection, then the memory is ready for immediate use, but thermal stress during connection causes charge loss in pre-programmed cells
Solution Approach 1:
The patent performs preliminary detection and verification of pre-programmed data before the memory device is fully operational. By checking for charge loss early in the initialization process and identifying affected cells before they cause read errors, the system can re-program critical data while the device is still being set up, ensuring data integrity from the start.
Solution Approach 2:
The patent implements protective measures by creating redundancy in pre-programmed data. Before thermal stress can cause catastrophic charge loss, the system has already stored backup copies and established detection mechanisms that cushion against the harmful effects of thermal stress during the connection and initialization process.
Data Source
AI summary
Memories including a controller configured to cause the memory to read a plurality of memory cells using a read voltage having a particular voltage level, determine a number of memory cells of a first subset of memory cells of the plurality of memory cells having a particular data state in response to the read voltage having the particular voltage level, and in response to determining that the number of memory cells of the first subset of memory cells having the particular data state is less than a particular threshold, adjust the voltage level of the read voltage based on the number of memory cells of the first subset of memory cells having the particular data state, and re-read the plurality of memory cells using the read voltage having the adjusted voltage level.