Fuse Protection Capacitor Prevents Accidental Programming
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Solution Overview
Problem
Fuse systems in semiconductor dies face accidental programming due to power supply transients and lack of electrical isolation when using a shared power supply and fuse programming pad, leading to potential defects and reduced yield.
Innovation Solution
Incorporating a fuse protection capacitor and/or diode in the fuse system to prevent unintended programming by regulating voltage and blocking current during transients, ensuring robustness against power supply fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a shared power supply and fuse programming pad are used, then device complexity is reduced, but reliability deteriorates due to accidental programming from power supply transients
Solution Approach 1:
A protection circuit is introduced as an intermediary between the shared power supply pad and the fuse cell. This protection circuit includes a first switch (e.g., PFET11) controlled by a bias generator, and optionally a second switch (e.g., NFET52) for enhanced protection. The protection circuit mediates the power supply voltage, blocking transient spikes that could cause accidental fuse programming while allowing normal programming operations when controlled appropriately.
Solution Approach 2:
The bias generator provides preliminary protection by biasing the control input of the first switch to keep it in a non-conducting state during normal operation and power transients. This preliminary anti-action prevents harmful current from reaching the fuse cell before transients can occur. The control logic actively monitors and responds to power supply conditions to prevent accidental programming.
2Reliability
If electrical isolation is provided between power supply and fuse programming, then reliability improves, but device complexity increases
Solution Approach 1:
The protection circuit serves as an intermediary that provides electrical isolation between the power supply pad and the fuse cell. The first switch (PFET11) and optionally the second switch (NFET52) create an isolated path that blocks transient currents while allowing controlled programming current when the bias generator and control logic appropriately enable the switches. This isolation achieves reliability without requiring completely separate physical pads.
Solution Approach 2:
The protection circuit performs multiple functions: it provides electrical isolation during normal operation and power transients, enables controlled programming when activated, and maintains compatibility with the shared pad architecture. The bias generator and control logic work together to make the same circuit path serve both protection and programming functions, achieving multi-functionality that reduces overall device complexity.
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
The implementation of a fuse protection capacitor and/or diode enhances the reliability and yield of semiconductor dies by preventing accidental programming, reducing the risk of defects and improving the robustness of the fuse system to voltage transients.
Implementation Method 1
a fuse protection capacitor electrically connected between the first pad and a control input of the second switch. The fuse protection capacitor is operable to inhibit unintended programming of the fuse by adjusting a bias of the second switch in response to a change in a voltage of the first pad relative to a voltage of the second pad
Implementation Method 2
the biasing circuit includes a voltage regulator electrically connected between the first pad and the second pad and configured to generate a regulated voltage, and a programming logic circuit configured to generate the fuse programming signal based on the regulated voltage
Data Source
AI summary
Apparatus and methods for protection against inadvertent programming of fuse cells are provided herein. In certain configurations, a fuse system includes a fuse programming transistor, a cascode transistor, and a fuse cell electrically connected in series between a first pad and a second pad. The fuse system further includes a bias generator that controls an amount of current provided to the fuse cell based on biasing a gate of the fuse programming transistor and a gate of the cascode transistor. The fuse system further includes a fuse protection capacitor electrically connected between the first pad and the gate of the cascode transistor to prevent inadvertent programming of the fuse cell in response to an increase in voltage of the first pad relative to the second pad.