Bandgap Reference Calibration for Accurate Temperature Sensing
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Solution Overview
Problem
Bandgap voltage reference circuits exhibit significant temperature dependence, leading to inaccuracies in temperature measurement, particularly when a single calibration value is used across varying temperatures.
Innovation Solution
A dynamic calibration module adjusts the bandgap voltage reference circuit by adding or subtracting bits from a predetermined calibration value based on changes in PTAT voltage, using a trim circuit to control terminal connections on a sense-resistor, thereby maintaining accurate reference voltage across a range of temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single calibration value is used for the bandgap voltage reference circuit, then the device complexity is reduced, but the measurement precision deteriorates due to significant temperature dependence
Solution Approach 1:
The patent implements a dynamic calibration system where the calibration value is no longer fixed but changes automatically with temperature. The dynamic calibration module monitors temperature and adjusts the calibration value accordingly, transforming the static calibration approach into a dynamic one that adapts to varying thermal conditions, thereby resolving the contradiction between simplicity and precision.
Solution Approach 2:
The system employs feedback mechanisms where the temperature measurement is continuously monitored and used to adjust the calibration value of the bandgap voltage reference circuit. This closed-loop feedback ensures that the calibration remains accurate across different temperature ranges without requiring manual intervention or complex fixed calibration circuits.
2Measurement precision
If a dynamic calibration module is implemented to adjust calibration values based on temperature, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The dynamic calibration module is segmented into distinct functional blocks: a temperature sensing unit, a calibration value storage unit with multiple predetermined values, and a selection unit that switches between calibration values based on temperature ranges. This segmentation allows the complex functionality to be organized into manageable modules, reducing the perceived complexity while maintaining high measurement precision.
Solution Approach 2:
Multiple predetermined calibration values are pre-calculated and stored in the calibration circuit for different temperature ranges. Instead of performing complex real-time calculations, the system simply selects from pre-prepared calibration values based on the current temperature, which simplifies the runtime operation while maintaining accuracy across varying temperatures.
3Measurement precision
If multiple predetermined calibration values are stored for different temperature ranges, then the measurement precision across temperature ranges is improved, but the quantity of substance (storage requirements) increases
Solution Approach 1:
Instead of storing calibration values for every possible temperature increment, the system stores calibration values only for key temperature ranges or thresholds. This partial approach provides sufficient precision for practical temperature measurement applications without the excessive storage requirements of a complete temperature-to-calibration mapping, resolving the contradiction between accuracy and storage needs.
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 ensures precise temperature measurement by dynamically calibrating the bandgap voltage reference circuit, reducing voltage reference variations and enhancing accuracy over a wide temperature range.
Implementation Method 1
a proportional to absolute temperature, PTAT, circuit configured to provide a PTAT voltage comprising a voltage proportional to absolute temperature
Implementation Method 2
a bandgap voltage reference circuit, BGVR circuit, configured to generate a voltage across a sense-resistor wherein a reference voltage is provided between a first terminal and a second terminal of the BGVR circuit
Data Source
AI summary
An apparatus for determining temperature including a PTAT circuit configured to provide a PTAT voltage proportional to absolute temperature, a bandgap voltage reference circuit configured to generate a voltage across a sense-resistor wherein a reference voltage is provided between a first terminal and a second terminal which couple to the sense-resistor, and a calibration circuit, including a memory to store a predetermined calibration value, a trim circuit to receive a trim value based on the predetermined calibration value to control where one or both of the first and second terminals couple to the sense-resistor for provision of the reference voltage, and a dynamic calibration module configured to, based on a change in the PTAT voltage, generate the trim value by adding or subtracting a predetermined number of bits from the predetermined calibration value. The apparatus provides a signal indicative of temperature based on the PTAT voltage and the reference voltage.