Temperature Tamper Detection Circuit Scaling for Room-Temperature Testing
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Solution Overview
Problem
Existing temperature tamper detection circuits in integrated circuits (ICs) face challenges in testing their operation effectively, as they require exposure to extreme temperatures outside the expected operating range, making it impractical and inconvenient to verify their functionality, especially when testing at room temperature is desired.
Innovation Solution
A circuit and method that scale the base-emitter voltage and delta base-emitter voltage to lie within a voltage reference range less than the supply voltage, allowing for testing of the integrated circuit temperature sensor within the expected operating temperature range, using a multiplexer and comparator to select and compare these voltages against reference voltages, enabling detection of temperature deviations without exposing the IC to extreme temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If extreme temperatures are applied to test the temperature tamper detector, then the detector operation can be verified, but the testing process becomes impractical and inconvenient
Solution Approach 1:
The patent transforms the testing approach by changing the temperature parameter from extreme values to room temperature. It achieves this by scaling the voltage signals (Vbe and delta Vbe) that represent temperature information, allowing the detector to be tested at convenient temperatures while still verifying its ability to detect extreme temperature conditions through the scaled voltage relationships
Solution Approach 2:
The patent creates a scaled-down copy of the temperature detection signals. Instead of physically exposing the detector to extreme temperatures, it uses scaled versions of the base-emitter voltages (Vbe and delta Vbe) that replicate the electrical behavior the detector would exhibit at extreme temperatures, enabling indirect verification of detector operation
2Ease of operation
If the base-emitter voltage and delta base-emitter voltage are scaled to lie within a voltage reference range, then testing can be performed at room temperature, but additional scaling circuitry is required
Solution Approach 1:
The scaling circuit is designed to serve multiple functions: it scales both Vbe and delta Vbe signals, provides the appropriate voltage reference range for comparison, and enables testing across different temperature conditions. This multi-functionality reduces the need for separate dedicated circuits for each signal, thereby minimizing the overall increase in device complexity
Solution Approach 2:
The scaling circuit acts as an intermediary between the temperature sensor outputs (Vbe and delta Vbe) and the comparator that evaluates them against reference voltages. It transforms the raw voltage signals into a standardized range that can be conveniently tested at room temperature while maintaining the proportional relationships necessary for accurate temperature detection
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
Enables effective testing and programming of temperature tamper detection circuits at room temperature or any convenient temperature within the operating range, ensuring accurate detection of temperature deviations and preventing unauthorized access to sensitive data without the need for generating extreme temperatures.
Implementation Method 1
the base-emitter voltage being a voltage across the base-emitter of a bipolar transistor of the integrated circuit and the delta base-emitter voltage being the difference between two base-emitter voltages based on different current densities
Data Source
Figure 1A~2A
Figure 1B~2B
Figure 3A
AI summary
An integrated circuit temperature sensor includes a sensing circuit operable to determine whether the integrated circuit is currently exposed to one of a relatively low temperature or a relatively high temperature. A selection circuit operates to select a measured voltage across the base-emitter of a bipolar transistor of the integrated circuit if the sensing circuit indicates that the integrated circuit is currently exposed to the relatively low temperature or, alternatively, select a measured delta voltage across the base-emitter of the bipolar transistor of the integrated circuit if the sensing circuit indicates that the integrated circuit is currently exposed to the relatively high temperature. A comparator then compares the selected measured voltage across the base-emitter of the bipolar transistor against a first reference voltage indicative of a too cold temperature condition or compares the selected measured delta voltage across the base-emitter of the bipolar transistor against a second reference voltage indicative of a too hot temperature condition. As a result of the comparison, detection may be made as to whether the integrated circuit is currently exposed to one of either a too cold or too hot temperature. In a test mode, the circuit is exposed to a readily available temperature, such as room temperature, and the measured delta voltage across the base-emitter and/or the measured voltage across the base-emitter are scaled in accordance with that available temperature for application to the comparator. Alternatively, in test mode the reference voltages are scaled to intersect with the measured delta voltage across the base-emitter and/or the measured voltage across the base-emitter at the available temperature.