Memory System Read Bias Voltage Control for Filled Unfilled Blocks
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In memory devices with increasing numbers of word lines, the distribution characteristic of memory cells can be distorted when not all word lines are filled, leading to read bias issues and potential read failures, especially when transitioning between filled and unfilled blocks.
Innovation Solution
The memory system groups word lines into multiple groups and adjusts the read bias voltage based on the amount of data programmed in each group, using flag cells to determine the program state of each group and optimize the read bias for stable operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of word lines is increased to achieve high density/high capacity, then memory capacity is improved, but read bias distortion occurs when word lines are not fully filled
Solution Approach 1:
The memory device divides word lines into multiple groups (first group, second group, etc.) and applies different read bias voltages to each group based on their program state. This segmentation allows the system to handle mixed filled/unfilled states within blocks, resolving the read bias distortion problem while maintaining high density.
Solution Approach 2:
The read bias voltage is dynamically adjusted based on the program state of each word line group. The memory controller determines whether each group is filled or unfilled and applies appropriate bias voltages (first read bias for filled groups, second read bias for unfilled groups), enabling adaptive compensation for distribution characteristic changes.
2Reliability
If read bias is adjusted for each word line group based on program state, then read operation reliability is improved, but device complexity increases
Solution Approach 1:
Flag cells are programmed in advance to indicate the program state of each word line group. During read operations, the memory controller simply reads these pre-prepared flag cells to determine which bias voltage to apply, avoiding complex real-time analysis of program states and simplifying the control logic.
Solution Approach 2:
Flag cells serve as intermediary indicators that store program state information for each word line group. These flag cells act as a buffer between the complex program state and the read control logic, allowing the controller to make simple binary decisions (filled/unfilled) based on flag cell values without directly analyzing the actual data state.
Data Source
AI summary
A memory device may include: a memory cell array comprising a plurality of search regions, each of the search regions comprising a plurality of group regions, each of the group regions comprising a flag cell, each flag cell comprising information indicating whether the corresponding group region is programmed; a voltage generator suitable for generating a read bias voltage for the memory cell array according to a voltage control signal; and a memory controller suitable for selecting a search region and controlling the voltage generator to adjust the read bias voltage based on information of flag cell of the selected search region when a read command is received, and controlling a read operation for the selected search region based on the adjusted read bias voltage.