CMOS Temperature Sensor for Image Sensors
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Solution Overview
Problem
Existing temperature sensors, such as thermistor-based circuits, are not suitable for low-power applications like cell phones due to high power consumption, require a stable and temperature-independent voltage source, and have large circuit elements that are not well-suited for integration into micro-circuits, with slow temperature response for some applications.
Innovation Solution
A fully integrated, solid-state temperature sensor fabricated using CMOS technology that produces an output current proportional to temperature, with a tunable zero crossing independent of output gain, requiring fewer components and lower power consumption, suitable for integration into small electronic devices like multi-pixel imaging sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If thermistor-based temperature sensing circuits are used, then temperature sensing capability is achieved, but power consumption is too high for low-power applications
Solution Approach 1:
The patent replaces the mechanical/physical thermistor-based voltage divider circuit with an integrated CMOS electronic circuit that uses transistor current mirrors and differential amplifiers to sense temperature, thereby reducing power consumption while maintaining sensing capability
Solution Approach 2:
The patent changes the operating parameters by using current-mode signaling instead of voltage-mode, and by operating transistors in specific regions (saturation, triode) to achieve low-power temperature sensing with improved energy efficiency
2Device complexity
If thermistor-based circuits are used, then temperature sensing is achieved, but large circuit elements are required that are not well suited for integration into micro-circuits
Solution Approach 1:
The patent merges multiple functions (temperature sensing, signal amplification, and output generation) into a single integrated CMOS circuit block, eliminating the need for discrete large circuit elements and enabling direct integration into micro-circuits
Solution Approach 2:
The CMOS circuit serves multiple functions simultaneously - it senses temperature, amplifies the signal through differential stages, and provides calibrated output - making it a universal building block suitable for integration into various micro-circuit applications
3Measurement precision
If stable and temperature-independent voltage source is used, then accurate temperature sensing is achieved, but additional components and complexity are required
Solution Approach 1:
The circuit uses its own internal current sources and transistor characteristics to automatically compensate for temperature variations, eliminating the need for external stable voltage sources while maintaining measurement precision through self-calibration mechanisms
Solution Approach 2:
The differential amplifier configuration provides inherent feedback that compares transistor voltages and adjusts the output to compensate for temperature drift, achieving accurate temperature sensing without requiring additional temperature-independent reference components
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 provides a low-power, compact temperature sensor with stable zero-crossing output independent of gain settings, suitable for integration into small devices, offering improved performance and efficiency in temperature monitoring.
Implementation Method 1
The temperature sensor uses a temperature-sensing circuit to produce a first output that is a function of temperature
Data Source
AI summary
An integrated temperature sensor provides an output current proportional to temperature rising from a zero value at a selectable reference temperature. The reference temperature can be selected by varying resistive values in the sensor's circuit. The temperature sensor can be manufactured at low cost and fully integrated on a chip using CMOS technology, and may be used for low-power applications.