Temperature Sensor Circuit PTAT CTAT Linearity
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Solution Overview
Problem
Existing temperature sensor circuits in electronic circuitry face challenges with DAC code-to-temperature non-linearity issues, leading to poor temperature measurement accuracy over a wide temperature range, particularly due to the use of proportional to absolute temperature (PTAT) and complementary to absolute temperature (CTAT) voltage approaches.
Innovation Solution
A temperature sensing circuit that utilizes the difference between PTAT and CTAT voltages to provide a linear temperature measurement, eliminating the need for a temperature-independent reference voltage and reducing offset and gain errors in analog-to-digital converters, by generating both voltages and using them to calculate a difference voltage that is directly proportional to temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DAC-based temperature sensing using PTAT and CTAT voltages is implemented, then temperature monitoring capability is provided, but code-to-temperature non-linearity occurs resulting in poor measurement accuracy
Solution Approach 1:
The patent changes the measurement parameter from direct voltage comparison to measuring the difference between PTAT and CTAT voltages. This parameter transformation creates a linear relationship between the voltage difference and temperature, eliminating the non-linearity inherent in DAC-based approaches while maintaining temperature monitoring capability
Solution Approach 2:
The patent introduces an intermediary measurement approach by using the difference voltage between PTAT and CTAT as a mediator. This intermediate parameter provides a linear mapping to temperature, serving as a bridge between the non-linear DAC codes and accurate temperature measurement
2Measurement precision
If PTAT and CTAT voltage approaches are used for temperature sensing, then temperature dependency measurement is achieved, but reference voltage fluctuations introduce offset and gain errors
Solution Approach 1:
The patent applies the counterweight principle by using CTAT voltage to compensate for the temperature-dependent variations in PTAT voltage. The difference between these two opposing temperature dependencies creates a signal that is linearly proportional to temperature and immune to reference voltage fluctuations, effectively canceling out the harmful effects
Solution Approach 2:
The patent implements a feedback mechanism where the difference between PTAT and CTAT voltages is measured and used to determine temperature. This feedback approach continuously monitors the temperature-dependent voltage variations and converts them into accurate temperature readings, compensating for reference voltage instabilities
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 solution achieves more accurate temperature measurement with a higher voltage difference per degree Celsius, improving linearity and reducing errors associated with reference voltage fluctuations, thereby enhancing the reliability of temperature monitoring in electronic circuitry.
Implementation Method 1
the temperature dependency is either proportional to absolute temperature ('PTAT'), wherein the measuring circuit outputs a voltage that increases in proportion to a rise in temperature
Implementation Method 2
or complementary to absolute temperature ('CTAT'), wherein the measuring circuit outputs a voltage that decreases in proportion to a rise in temperature
Data Source
AI summary
A temperature sensor circuit implemented in electronic circuitry that senses the temperature at a site, digitizes the sensed temperature, and then outputs a signal representing such a sensed temperature. The temperature sensor circuit converts a voltage signal that is proportional to the temperature to a first digital value. The temperature sensor circuit converts a voltage signal that is inversely proportional to the temperature to a second digital value. The sensed temperature is determined as a function of a difference between the first and second digital values.