Flash Memory Programming Current Mirror Averaging
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Solution Overview
Problem
Existing methods for programming flash memory cells suffer from variability in bias current sources due to natural variations and manufacturing mismatches, leading to inconsistent current draw during the programming process, especially in advanced nanometer flash memory cells.
Innovation Solution
Averaging two or more current mirrors to draw current from each block in the memory array, and initializing each current mirror before operation using a capacitor to maintain a near-ideal state, thereby reducing variability and ensuring consistent current delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current mirrors are used to draw current from memory blocks during programming, then current delivery is enabled, but current variability increases due to manufacturing mismatches and natural variations
Solution Approach 1:
The patent combines multiple current mirrors (e.g., four current mirrors) to serve each memory block, rather than using a single current mirror. This merging approach averages out the manufacturing variations and mismatches inherent in individual current mirrors, thereby reducing overall current variability and improving delivery consistency across all memory blocks.
Solution Approach 2:
The patent changes the parameter of current mirror configuration from a single-unit system to a multi-unit averaged system. By modifying how current mirrors are structured and combined (using multiple mirrors in parallel with averaging), the system transforms the current delivery mechanism to compensate for manufacturing imperfections and achieve more consistent current across varying process conditions.
2Reliability
If multiple current mirrors are averaged to reduce current variability, then current consistency improves, but device complexity increases
Solution Approach 1:
The patent implements a universal current delivery architecture where multiple current mirrors serve multiple memory blocks in an averaged configuration. This multi-functional setup allows the same current mirror structure to be replicated and shared across different blocks, achieving current consistency without requiring entirely separate circuitry for each block, thereby managing complexity through systematic reuse.
3Measurement precision
If current mirrors are initialized before operation, then current accuracy improves, but programming time increases
Solution Approach 1:
The patent applies preliminary action by initializing current mirrors before they are used for programming operations. This preliminary initialization sets the current mirrors to accurate reference states, ensuring that subsequent programming operations benefit from precise current delivery. The trade-off of additional initialization time is accepted to achieve the necessary current accuracy for reliable programming.
Solution Approach 2:
The patent implements periodic initialization of current mirrors, where the initialization process is performed at regular intervals or before each programming operation. This periodic action ensures that current mirrors maintain their accuracy over time and across multiple programming cycles, with the initialization time distributed periodically rather than continuously, thereby managing the time trade-off systematically.
Data Source
AI summary
An improved method and apparatus for programming advanced nanometer flash memory cells is disclosed.