Memory Controller EPI-Based Voltage Adjustment
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Solution Overview
Problem
Long erase program intervals in flash memory devices lead to degraded threshold voltage distribution characteristics, reducing data reliability and causing inefficient storage and frequent garbage collection operations.
Innovation Solution
A memory controller and system that dynamically adjust operation conditions based on the erase program interval (EPI) by selecting between different program, verify, and read voltage levels to maintain data reliability, including a method to determine EPI and generate control information for voltage settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data is programmed after a long erase program interval (EPI), then storage efficiency is improved, but threshold voltage distribution characteristic degrades and data reliability decreases
Solution Approach 1:
The patent applies dynamics by making the program operation conditions adjustable based on the EPI value. The memory controller dynamically selects different program conditions (such as program voltage levels, verify voltage levels, number of program cycles) according to the measured EPI, allowing the system to adapt to varying time intervals between erase and program operations. This dynamic adjustment maintains data reliability across different EPI scenarios while preserving storage efficiency improvements.
Solution Approach 2:
The patent changes physical parameters of the program operation based on EPI. Specifically, it adjusts program voltage levels, verify voltage levels, and the number of program cycles as functions of the EPI value. When EPI exceeds a threshold, the system modifies these parameters to compensate for threshold voltage distribution degradation, thereby maintaining data reliability without sacrificing storage efficiency.
2Productivity
If data is programmed after a long erase program interval (EPI), then storage efficiency is improved, but threshold voltage distribution characteristic degrades
Solution Approach 1:
The system dynamically adjusts program operation parameters based on the EPI value to maintain threshold voltage distribution characteristics. By making the program conditions adaptive rather than fixed, the system can compensate for the degrading effect of long EPI on threshold voltage distribution while still benefiting from improved storage efficiency.
Solution Approach 2:
The patent modifies program voltage levels, verify voltage levels, and program cycle counts based on the EPI measurement. These parameter changes are specifically designed to counteract the threshold voltage distribution degradation caused by long EPI, thereby maintaining manufacturing precision in terms of threshold voltage control while preserving storage efficiency gains.
3Device complexity
If conventional program operation is used regardless of EPI, then device complexity is low, but data reliability degrades under long EPI conditions
Solution Approach 1:
The patent implements feedback by measuring the EPI value and using this information to adjust program operation conditions. The memory controller monitors the time interval between erase and program operations, then feeds this information back into the program control logic to select appropriate program conditions. This feedback mechanism maintains data reliability under varying EPI conditions while adding only moderate complexity to the control system.
Solution Approach 2:
The system performs self-service by automatically determining EPI and selecting appropriate program conditions without external intervention. The memory controller autonomously measures the time interval, evaluates whether it exceeds a threshold, and adjusts program parameters accordingly, eliminating the need for manual configuration or complex external control while maintaining data reliability.
Data Source
AI summary
Provided are a memory controller and memory system having an improved threshold voltage distribution characteristic and an operating method of the memory system. As a write request of data with respect to a first block is received, an erase program interval (EPI) is determined denoting a time period elapsed after erasure of the first block. When the determined EPI is equal to or less than a reference time, data is programmed to the first block based on a first operation condition selected from among a plurality of operation conditions. When the determined EPI is greater than the reference time, the data is programmed to the first block based on a second operation condition selected from among the plurality of operation conditions.