Self-Referenced BJT Temperature Sensing for Accurate Die Measurement
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Solution Overview
Problem
Existing methods for measuring die temperature in integrated circuits suffer from low accuracy and significant errors due to thermal gradients and leakage currents, particularly in System-on-Chip products with high power dissipation, and are limited by complex measurement and signal-conditioning circuitry.
Innovation Solution
The use of self-referenced, high-accuracy temperature sensors based on Bipolar Junction Transistors (BJTs) that minimize error sources through techniques such as dynamic element matching and parasitic resistance cancellation, allowing for precise die temperature measurement using on-chip Analog-to-Digital Converters and configurable circuit configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external temperature sensors such as thermocouples are used, then temperature measurement is possible, but measurement accuracy deteriorates due to thermal gradients between the silicon junction and sensor locus
Solution Approach 1:
The patent extracts the temperature sensing function from external sensors and integrates it directly into the silicon junction where temperature measurement is needed. This eliminates the thermal gradient problem by placing the sensing element exactly at the measurement point of interest, removing the need for external thermocouples or sensors that would require physical connection to the die.
Solution Approach 2:
The patent introduces an intermediary approach by using the silicon junction itself as the sensing element rather than a separate sensor. The junction temperature becomes the measurement target directly, using the existing semiconductor structure as both the device under test and the temperature sensor, thereby eliminating thermal gradient errors.
2Measurement precision
If fully integrated temperature sensors are used, then sensitivity to thermal gradients is improved, but measurement circuitry complexity increases
Solution Approach 1:
The patent extracts only the essential temperature sensing function from complex integrated sensor systems, using a simplified approach that relies on measuring voltage changes across the silicon junction without requiring elaborate signal conditioning circuits. This reduces complexity while maintaining sensitivity to thermal conditions.
Solution Approach 2:
The silicon junction serves itself as the temperature sensor, utilizing its inherent electrical properties (voltage-temperature relationship) without requiring external sensing elements or complex conditioning circuitry. The device under test provides its own temperature measurement capability through its natural electrical characteristics.
3Device complexity
If internal temperature sensors with pad output are used, then integration is improved, but measurement accuracy deteriorates due to leakage currents creating signal offsets
Solution Approach 1:
The patent extracts the temperature measurement signal from the problematic pad output interface and instead measures it through internal circuit nodes that are not susceptible to leakage currents. By taking the measurement path away from the pad, the solution eliminates the source of measurement error while maintaining integration benefits.
Solution Approach 2:
The patent introduces an intermediary measurement path that bypasses the leakage-prone pad interface. Instead of measuring directly at the pad where leakage occurs, the system uses internal circuit nodes as intermediaries to sense the temperature signal, thereby isolating the measurement from harmful leakage effects.
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 approach provides highly accurate die temperature measurement with reduced errors, suitable for both factory tests and field applications, while minimizing costs and silicon footprint, and is compatible with moderate-precision ADCs, achieving precision within ±1°C for production tests and ±3°C for field applications.
Implementation Method 1
employ thermal properties of Bipolar Junction Transistors ('bipolar transistors' or 'BJTs') to generate accurate temperature measurements
Data Source
AI summary
A sensor may include: a first plurality of resistors; a first BJT having: a first base terminal, a collector terminal, and an emitter terminal, where the collector terminal is coupled to the first plurality of resistors; and a first amplifier having a first non-inverting input coupled to the collector terminal and an output terminal coupled to the base terminal. The sensor may include: a second plurality of resistors; a second BJT having: a base terminal, a collector terminal, and an emitter terminal, where the base terminal is coupled to the base terminal of the first BJT, where the collector terminal is coupled to the second plurality of resistors; and a second amplifier having an inverting input coupled to the collector terminal and an output terminal coupled to the emitter terminal, wherein the inverting input terminal of the first amplifier is coupled to a non-inverting input terminal of the second amplifier.