CMOS Temperature Sensor Bandgap Reference Circuit Accuracy
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Solution Overview
Problem
CMOS temperature sensors face accuracy issues due to process variations during fabrication, affecting their performance in measuring semiconductor device temperatures.
Innovation Solution
A CMOS temperature sensor design incorporating a bandgap reference circuit that generates a temperature-proportional current and voltage, a reference voltage generator for correcting voltages, and a temperature information voltage generator, using BJTs and current sources to stabilize and correct temperature readings, thereby enhancing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional CMOS temperature sensor is used, then the device structure is simple and manufacturing is easy, but the measurement accuracy deteriorates due to process variations
Solution Approach 1:
The temperature sensor is divided into multiple functional modules: a bandgap reference circuit for generating temperature-compensated reference voltage, a reference current generator for providing stable reference currents, and a sensing circuit for measuring temperature. This segmentation allows each module to be optimized independently, improving overall measurement accuracy while managing complexity through modular design
Solution Approach 2:
A bandgap reference circuit is introduced as an intermediary component to generate a reference voltage that is compensated for temperature variations. This reference voltage serves as a stable benchmark against which temperature measurements are made, thereby improving measurement accuracy by eliminating the direct impact of process variations on the measurement process
2Measurement precision
If process variations are reduced to improve accuracy, then manufacturing precision must be increased, but this increases manufacturing cost and difficulty
Solution Approach 1:
The bandgap reference circuit provides a feedback mechanism that automatically compensates for temperature-induced variations in the sensor circuitry. By continuously monitoring and adjusting the reference voltage based on temperature changes, the system maintains high measurement accuracy without requiring stricter manufacturing tolerances
Solution Approach 2:
The circuit utilizes parameter changes in transistor characteristics with temperature to generate compensating signals. Specifically, the bandgap reference circuit exploits the temperature-dependent behavior of base-emitter voltages in bipolar transistors to create a reference voltage that remains stable across temperature ranges, thereby achieving high accuracy without improved manufacturing precision
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 high-accuracy temperature measurements by minimizing the impact of process variations and fluctuations, ensuring stable reference and temperature information voltages, and effectively converting analog signals to digital for precise temperature information.
Implementation Method 1
a bandgap reference circuit providing a bandgap reference voltage regardless of temperature using a first voltage inversely proportional to temperature and a second voltage proportional to temperature
Implementation Method 2
a bandgap reference circuit including a first BJT and a second BJT whose base terminals are connected to each other, the bandgap reference circuit generating a temperature-proportional current using a first voltage, which is a base-emitter voltage of the first BJT, and a second voltage based on a difference between the first voltage and a base-emitter voltage of the second BJT
Data Source
AI summary
A CMOS temperature sensor is provided. The CMOS temperature sensor, comprises: a bandgap reference circuit outputting a constant bandgap reference voltage regardless of temperature using a first voltage inversely proportional to temperature and a second voltage proportional to temperature and generating a first current proportional to temperature using the second voltage; a reference voltage generator copying the first current and outputting a reference voltage generated using the first voltage and the copied first current; and a temperature information voltage generator copying the first current and outputting a temperature information voltage proportional to temperature.