Bolometric On-Chip Temperature Sensor Self-Calibration
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Solution Overview
Problem
On-chip temperature sensors in silicon-on-insulator (SOI) technology require extra calibration measurements due to process tolerance, increasing implementation costs and limiting their use.
Innovation Solution
An improved on-chip temperature sensing circuit based on bolometry, featuring a temperature sensor, an identical reference sensor thermally coupled with a heater, and a comparator that drives the heater to match outputs, allowing self-calibration and accurate temperature measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pn junction diodes are used as temperature sensors in SOI technology, then temperature sensing capability is achieved, but process tolerance causes ideality factor variations requiring extra calibration measurements
Solution Approach 1:
The patent implements self-calibration by using a reference sensor and heater combination that automatically compensates for process variations. The reference sensor is thermally coupled to a heater, and by controlling the heater power, the system can calibrate itself without external calibration measurements, eliminating the need for manual calibration procedures while maintaining measurement accuracy.
Solution Approach 2:
The patent introduces a reference sensor as an intermediary element that serves as a calibration reference. This reference sensor, when combined with the heater, acts as a mediator to establish a known temperature reference point, allowing the measurement sensor to be calibrated against it without requiring external calibration equipment or procedures.
2Measurement precision
If extra calibration measurements are performed to account for process tolerance, then temperature measurement accuracy is improved, but implementation cost increases
Solution Approach 1:
The self-calibrating system eliminates the need for external calibration services or procedures, allowing the temperature sensor system to calibrate itself automatically. This reduces implementation costs by removing the requirement for specialized calibration equipment, trained personnel, and external calibration services, while maintaining high measurement accuracy through the reference sensor and heater mechanism.
3Adaptability or versatility
If pn junction diodes with n>1 are used in SOI technology, then temperature sensing is enabled, but process tolerance causes variability limiting widespread use
Solution Approach 1:
The patent employs feedback mechanisms where the reference sensor provides a stable reference signal that is compared against the measurement sensor output. The heater control system uses feedback to maintain the reference sensor at a known temperature, and this feedback loop compensates for process variations, ensuring consistent and reliable temperature measurements across different manufacturing batches and conditions.
Solution Approach 2:
The reference sensor acts as an intermediary that mediates between the measurement sensor and the varying process conditions. By providing a stable reference point that is less sensitive to process variations, it enables the system to achieve consistent measurement results despite variations in the ideality factor and other process parameters.
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 solution enables accurate temperature measurement without additional calibration, reducing costs and variability across manufacturing processes, and improving temperature monitoring for improved circuit operation.
Implementation Method 1
a heater that is thermally coupled to the reference sensor and driven by the output current from the comparator
Implementation Method 2
pn junction diodes have been used because of the nearly ideal behavior of the forward conduction state in such pn junction diodes. That is, j=j0 exp(Vf Qe/(n k T))
Implementation Method 3
The comparator is adapted to receive and compare the outputs from both the temperature and reference sensors
Data Source
AI summary
Disclosed are embodiments of an improved on-chip temperature sensing circuit, based on bolometry, which provides self calibration of the on-chip temperature sensors for ideality and an associated method of sensing temperature at a specific on-chip location. The circuit comprises a temperature sensor, an identical reference sensor with a thermally coupled heater and a comparator. The comparator is adapted to receive and compare the outputs from both the temperature and reference sensors and to drive the heater with current until the outputs match. Based on the current forced into the heater, the temperature rise of the reference sensor can be calculated, which in this state, is equal to that of the temperature sensor.