Flash Memory Dummy Cells as Source Line Pull Down Circuits
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Solution Overview
Problem
Existing flash memory systems require high voltage transistors for source line pull down circuits, which occupy die space, increase complexity and cost, and are prone to overstress and breakdown during programming.
Innovation Solution
Utilizing dummy memory cells as source line pull down circuits, which operate within the same voltage range as the memory cells and distribute the pull down current among multiple cells, reducing electromagnetic interference and current drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high voltage transistors are used for source line pull down circuits, then source line grounding function is achieved, but die space is occupied and device complexity increases
Solution Approach 1:
Dummy memory cells that were previously non-functional or unused are repurposed to serve as source line pull down circuits. These cells perform their original memory function while simultaneously providing the source line grounding function, eliminating the need for separate high voltage transistors and reducing die space.
Solution Approach 2:
The dummy memory cells serve themselves by using their inherent transistor structures to perform the pull down function. The cells' own transistors are utilized to ground the source line, eliminating the need for external dedicated pull down transistors and reducing overall device complexity.
2Reliability
If high voltage transistors are used for source line pull down circuits, then source line grounding is achieved, but device complexity and cost increase
Solution Approach 1:
The dummy memory cells integrate multiple functions: they serve as memory storage elements and simultaneously function as pull down circuits. This consolidation reduces the number of separate components and simplifies the bias and logic control circuits that would otherwise be needed to manage dedicated pull down transistors.
Solution Approach 2:
The invention changes the operational parameters of dummy memory cells from inactive or alternative uses to active participation in source line control. By adjusting voltage levels and control signals, the dummy cells are configured to perform pull down operations, leveraging existing cell structures rather than requiring specialized high voltage transistor designs.
3Area of stationary object
If dummy memory cells are used as source line pull down circuits, then die space is reduced and robustness is enhanced, but current distribution among multiple cells must be managed
Solution Approach 1:
The pull down function is segmented across multiple dummy memory cells rather than concentrated in a single high voltage transistor. Each dummy cell contributes a portion of the total pull down current, distributing the electrical stress and improving robustness. The segmented approach naturally divides the current load among parallel cell structures.
Solution Approach 2:
The dummy memory cells act as intermediary elements between the source line and ground. By routing current through these cells, the system achieves distributed current management where each cell serves as an intermediate conductive path, naturally balancing the current distribution through their parallel configuration.
Data Source
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AI summary
The present invention relates to a flash memory device that uses dummy memory cells as source line pull down circuits.