Dynamic Bandgap Calibration for Accurate PTAT Temperature Sensing
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Solution Overview
Problem
Bandgap voltage reference circuits exhibit significant temperature dependence, leading to inaccuracies in temperature measurement due to their inherent curvature in voltage output over temperature ranges, which existing calibration methods fail to adequately address, especially in applications requiring precise temperature sensing.
Innovation Solution
An apparatus incorporating a dynamic calibration module that adjusts the trim value of a bandgap voltage reference circuit by adding or subtracting bits from a predetermined calibration value based on detected changes in PTAT voltage, allowing for real-time calibration and improved temperature measurement accuracy across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bandgap voltage reference circuit is used to generate a reference voltage, then the reference voltage has a small temperature dependence, but the circuit exhibits significant temperature dependence with curvature in voltage output over temperature ranges leading to inaccuracies in temperature measurement
Solution Approach 1:
The patent implements dynamic calibration by making the trim value adjustable in real-time based on detected PTAT voltage changes. The calibration circuit continuously monitors the PTAT voltage and modifies the trim value accordingly, transitioning from a static reference voltage approach to a dynamic one that adapts to temperature variations, thereby resolving the contradiction between reliability and measurement precision.
Solution Approach 2:
The patent employs feedback mechanisms where the PTAT voltage is detected and fed back to the calibration circuit. The calibration circuit uses this feedback to determine when calibration is needed and adjusts the trim value of the bandgap voltage reference circuit accordingly. This closed-loop feedback system ensures that the reference voltage remains accurate across varying temperatures, addressing the precision issue while maintaining reliability.
2Manufacturing precision
If existing calibration methods are used for the bandgap voltage reference circuit, then the circuit can be calibrated, but the calibration fails to adequately address the curvature issue across wide temperature ranges
Solution Approach 1:
The patent transforms the static calibration process into a dynamic one by implementing continuous monitoring of PTAT voltage and real-time adjustment of the trim value. This dynamic calibration approach allows the circuit to adapt to different temperature ranges during operation, not just at a fixed calibration point, thereby improving both manufacturing precision and temperature range adaptability.
Solution Approach 2:
The patent changes the operating parameters of the bandgap voltage reference circuit by dynamically adjusting the trim value based on detected PTAT voltage changes. This parameter adjustment allows the circuit to maintain accuracy across wide temperature ranges by modifying the reference voltage characteristics in response to temperature variations, enhancing both calibration accuracy and temperature adaptability.
3Measurement precision
If a trim circuit is added to adjust the reference voltage, then calibration capability is improved, but the device complexity increases
Solution Approach 1:
The patent integrates multiple functions into the calibration circuit, which not only trims the reference voltage but also monitors PTAT voltage, determines calibration needs, and adjusts trim values dynamically. By making the calibration circuit multi-functional, the patent improves reference voltage accuracy without proportionally increasing device complexity, as the same circuit structure performs multiple critical functions.
Solution Approach 2:
The calibration circuit is designed to automatically monitor the PTAT voltage and adjust the trim value without external intervention. The circuit self-calibrates by detecting voltage changes and autonomously modifying its own parameters, which improves measurement precision while minimizing the need for additional control circuitry or manual calibration mechanisms, thereby limiting the increase in device complexity.
Data Source
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AI summary
An apparatus for determining temperature comprising: 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; a calibration circuit, comprising: 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; 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; wherein the apparatus provides a signal indicative of temperature based on the PTAT voltage and the reference voltage.