Fuse Sense Circuit Using Multiple Reference Resistances
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Solution Overview
Problem
Existing methods for sensing the state of fusible links in electronic circuits lack reliability, particularly in distinguishing between unblown and blown fuses, especially due to manufacturing variations and defects, leading to potential misclassification during testing.
Innovation Solution
A sense circuit and method utilizing multiple independently selectable reference resistances to compare against the resistance of a fuse, allowing for increased error margins and accurate determination of the blown or unblown state through various combinations of reference resistances, including parallel and series configurations, and the use of variable resistance devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single reference resistor is used to compare against fuse resistance, then the sensing circuit is simple, but the reliability of fuse state determination is insufficient due to manufacturing variations and defects
Solution Approach 1:
The patent divides the sensing function into multiple independent reference resistors (first reference resistor and second reference resistor) with different resistance values. Each reference resistor performs a specific comparison function, segmenting the sensing task to improve reliability without creating a single point of failure.
Solution Approach 2:
The patent uses reference resistors with different resistance values (parameters) to compare against the fuse resistance. By changing the reference resistance parameter, the circuit can determine different fuse states (unblown, partially blown, completely blown) based on the voltage difference comparisons, thereby improving determination reliability.
2Measurement precision
If the reference resistor value is set to distinguish blown and unblown fuses, then the sensing range is adequate, but the error margin between manufacturing screening and end-use testing is insufficient
Solution Approach 1:
The patent segments the measurement range by using multiple reference resistors with different resistance values. The first reference resistor handles one range of fuse resistance values while the second reference resistor handles another range, creating segmented measurement zones that improve both precision and error margin coverage.
Solution Approach 2:
The patent applies partial action by using different reference resistors for different testing stages. The first reference resistor is optimized for manufacturing screening while the second reference resistor provides additional margin for end-use testing, ensuring that each stage has adequate measurement precision without requiring the full range in a single component.
3Reliability
If multiple reference resistors are used to increase error margin, then the reliability of fuse state determination is improved, but the device complexity increases
Solution Approach 1:
The patent merges multiple reference resistors into a unified sensing circuit architecture that shares common elements (current source, voltage measurement mechanism, logic circuit). This combining approach allows multiple reference resistors to improve reliability while minimizing the increase in overall device complexity through resource sharing.
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
Enhances the reliability of fuse state determination by providing a greater margin of error between manufacturing screening and end-use testing, ensuring accurate identification of fuse states even in the presence of manufacturing variations and defects, and allows for programming and calibration of circuit settings.
Implementation Method 1
Unblown fuse resistance may typically be less than 100 ohms, whereas blown fuse resistance may be anywhere from 700 ohms if blown incompletely (i.e., partially blown) to somewhere between 4000 ohms and infinity (i.e., an open circuit) if blown completely.
Data Source
AI summary
A sense circuit and method for use in measuring the blown or unblown state of fusible links (fuses), particularly in integrated circuits. Embodiments include at least one additional reference resistance to allow for a greater margin of error in determining the actual state of a fuse. By having two or more reference resistances that can be independently selectable, additional combinations of reference resistance values are available to compare against the resistance of a fuse being tested.