Irreversible Snapback Fuse Cell for Simplified One-Time Programming
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Solution Overview
Problem
Existing solutions for programmable circuit blocks, such as EEPROM cells and traditional fuse cells, face challenges in complexity and space consumption, especially when programming needs to be done only once, as they require intricate circuitry and processes for reliable programming.
Innovation Solution
An anti-fuse type fuse cell utilizing an irreversible snapback device like NMOS, NPN bipolar transistor, or SCR, which is connected between power supply and ground, with controlled bias to induce irreversible snapback mode for programming, creating a low resistance path after programming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fuse cells are used with CMOS switch circuit for programming, then the fuse cell can be programmed by burning out, but the programming circuit becomes complex and the process becomes sophisticated
Solution Approach 1:
The patent extracts the programming function from a complex CMOS switch circuit and integrates it directly into the fuse cell structure itself. The fuse cell now contains an NMOS transistor with gate connected to drain, eliminating the need for external pulsed switch circuitry while maintaining reliable burnout capability.
Solution Approach 2:
The patent merges the fuse element and the programming switch into a single integrated structure. The NMOS transistor's gate is connected to its drain, combining the switching function and the fuse function into one device, thereby simplifying the overall circuit complexity.
2Adaptability or versatility
If EEPROM cells are used for programmable blocks, then the block can be programmed, but additional complex programming circuitry is required and substantial space is consumed
Solution Approach 1:
The patent uses a disposable fuse cell that is programmed once by burning out the NMOS transistor. This one-time programming approach eliminates the need for complex re-programmable circuitry while consuming minimal space, as the fuse cell structure itself is compact and does not require additional programming circuitry.
3Ease of operation
If on-chip programming is implemented with traditional fuse cells, then programming can be done on-chip, but a rather complex pulsed switch circuit is required
Solution Approach 1:
The fuse cell is designed to be self-programming through its intrinsic structure. The NMOS transistor with gate connected to drain automatically functions as the programming switch, eliminating the need for external pulsed switch circuitry. The cell programs itself when appropriate voltages are applied, simplifying the on-chip programming implementation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution simplifies the programming process by ensuring reliable burnout with minimal circuit complexity and space usage, allowing for efficient one-time programming with the ability to retry if necessary, while maintaining a low resistance path post-programming.
Implementation Method 1
the device to go into snapback mode... causing the device to go into snapback mode
Implementation Method 2
programmed by burning the fuse cell out... ensuring reliable burn out of the fuse cell
Data Source
AI summary
In a programmable circuit making use of fuse cells, a snapback NMOS or NPN transistor or SCR without reversible snapback capability is used as an anti-fuse, and programming comprises biasing the control electrode of the transistor to cause the transistor to go into snapback mode.