PTAT Current Temperature Sensing for Fast High-Resolution Readout
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Solution Overview
Problem
Existing temperature measurement techniques, such as resistor-based and diode-based methods, face limitations in accuracy, speed, and resolution, leading to slow response times and linearity issues.
Innovation Solution
A temperature measurement system utilizing a Proportional to Absolute Temperature (PTAT) current source, a capacitor, and an analog-to-digital converter (ADC) to charge the capacitor for a controlled time, allowing for precise voltage measurement and calculation of temperature, with optional Zero Change to Absolute Temperature (ZTAT) current sink and current mirror circuits for enhanced current handling and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistor-based temperature measurement is used, then temperature can be measured, but accuracy and conversion speed are limited
Solution Approach 1:
The patent replaces traditional resistor-based voltage measurement with a current-based measurement system. A PTAT current source generates a current directly proportional to absolute temperature, which is then measured by an ADC. This substitution of measurement methodology eliminates the need for precision resistors and voltage division, achieving both high accuracy (0.05°C resolution) and fast conversion speed (625 ns charging time) simultaneously.
2Measurement precision
If diode-based temperature measurement is used, then temperature can be measured, but response time is slow and resolution is low
Solution Approach 1:
The patent changes the fundamental measurement parameter from voltage (in diode-based methods) to current. By using a PTAT current source that directly outputs current proportional to temperature, the system achieves linear temperature measurement without the exponential characteristics of diode voltage. This parameter change enables both high resolution (0.05°C) and fast response (625 ns) by eliminating the slow charging characteristics of diode-based approaches.
3Measurement precision
If resistor divider technique is used, then temperature measurement is possible, but response time is slow and linearity is poor
Solution Approach 1:
The patent replaces the resistor divider voltage-based approach with a direct current-based measurement system. The PTAT current source provides a current that is linearly proportional to temperature, eliminating the need for resistor dividers and their associated linearity corrections. The fast ADC conversion of this current signal achieves both superior linearity and rapid response time compared to traditional voltage-divider methods.
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 system achieves high-resolution temperature measurement with fast response times, improved accuracy, and reduced noise, enabling precise temperature determination with resolutions down to less than 0.05°C and charging times as short as 625 ns.
Implementation Method 1
a proportional to absolute temperature (PTAT) current source
Implementation Method 2
a capacitor selectively coupled to the PTAT current source by a controllable switch
Data Source
AI summary
A Proportional-To-Absolute-Temperature (PTAT) current source is used for high-resolution temperature measurement. The PTAT current source is coupled to a capacitor for a fixed amount of time so as to charge the capacitor to a voltage which is proportional to the current applied to the capacitor, and thus proportional to the temperature. The voltage on the capacitor is measured, and a temperature is calculated or determined from the measured voltage.