E-fuse Circuit for Controlled Lifetime and Tamper Resistance
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Solution Overview
Problem
Modern semiconductor chips with long service lifetimes pose challenges in applications requiring controlled or limited lifespan, as well as the risk of unauthorized use or tampering, as existing methods like warranty voiding stickers are ineffective.
Innovation Solution
A circuit with a critical element that can transition from an enable state to a disable state based on predefined conditions, using triggers such as counters, comparators, sensors, or signal receivers to prevent normal operation when specific conditions are met, allowing for controlled operation and tamper resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a circuit is designed with long service lifetime and high reliability, then the circuit performs well in most applications, but it cannot be disabled when needed and may be used unauthorized
Solution Approach 1:
The circuit transitions from a static design to a dynamic one by incorporating a critical element that can change state between enabled and disabled. This allows the circuit's service lifetime to be controlled dynamically rather than being fixed, resolving the contradiction between long service life and controllable disablement.
Solution Approach 2:
The invention changes the operational parameter of the critical element from always-conductive to selectively-conductive. By modifying the electrical state of the critical element based on trigger conditions, the circuit achieves adaptable service life while maintaining high reliability during authorized operation.
2Object-affected harmful factors
If a sticker warning is placed on the housing to prevent tampering, then the warning is visible, but it is ineffective in preventing unauthorized use
Solution Approach 1:
The critical element acts as an intermediary between the circuit and potential tampering attempts. Instead of relying on external warnings, the circuit incorporates an internal protective mechanism that automatically responds to tamper conditions, making tamper resistance effective rather than symbolic.
Solution Approach 2:
The circuit is designed with preliminary protective measures where the critical element is configured to detect tamper conditions and automatically disable the circuit before unauthorized use can occur. This preemptive approach prevents tampering rather than merely warning against it.
3Adaptability or versatility
If a critical element is added to enable/disable the circuit based on conditions, then controlled operation is achieved, but the device complexity increases
Solution Approach 1:
The invention extracts the control function into a separate critical element that can be independently configured and triggered. This modular approach allows controlled operation to be added without fundamentally redesigning the entire circuit, managing complexity by separating concerns.
Data Source
AI summary
An apparatus for disabling a circuit when the circuit is in a first preselected condition includes a critical element that has an enable state and a disable state. The critical element is configured in relation to the circuit such that the circuit cannot operate normally if the critical element is in the disable state. A trigger generates a state signal that causes the critical element to enter the disable state when a comparison of a current condition to a stored value indicates that the circuit is in the first preselected condition. In a method of controlling operation of a circuit, a current condition is sensed. Whether the current condition corresponds to a stored value is determined. If the current condition corresponds to the stored value, then a critical element is caused to enter a disable state so that the circuit is prevented from operating normally.