Current-Mode Thermal Sensor Circuit Design
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Solution Overview
Problem
Existing temperature sensor circuits in computer systems are limited by large area consumption on integrated circuits and accuracy issues due to sensitivities to power supply voltage variation and device variation, requiring additional trimming processes.
Innovation Solution
The proposed solution involves processing a current proportional to absolute temperature (PTAT) and a current complementary to absolute temperature (CTAT) using an analog feedback loop, eliminating the need for analog-to-digital conversion circuits and bandgap reference circuits, thereby reducing circuit area and trimming requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional temperature sensor circuits are used, then temperature detection function is achieved, but circuit area is large and accuracy is limited due to power supply voltage variation and device variation
Solution Approach 1:
The patent extracts and eliminates the bandgap reference circuit and analog-to-digital conversion circuit from the traditional temperature sensor architecture. By removing these complex components and using only PTAT and CTAT current sources with a comparator, the circuit complexity is reduced while maintaining temperature measurement functionality.
Solution Approach 2:
The patent changes the operating parameters by using current-mode operation instead of voltage-mode operation. The temperature sensor generates PTAT and CTAT currents that are compared to determine temperature, avoiding the need for voltage references and ADC circuits, thereby improving accuracy while reducing complexity.
2Measurement precision
If traditional temperature sensor circuits with bandgap reference and ADC are used, then accurate temperature measurement is achieved, but circuit area is large
Solution Approach 1:
The patent removes the bandgap reference circuit and analog-to-digital conversion circuit from the temperature sensor design. These extracted components are replaced by a simpler current comparison approach using PTAT and CTAT current sources, significantly reducing the circuit area while preserving measurement accuracy.
Solution Approach 2:
The patent merges the temperature sensing and comparison functions into a single integrated circuit block. The PTAT current source, CTAT current source, and comparator are combined in one unit, eliminating the need for separate bandgap reference and ADC circuits, thereby reducing overall circuit area.
3Reliability
If traditional sensor circuits are used, then temperature detection is achieved, but additional trimming processes are required due to device variation sensitivity
Solution Approach 1:
The patent changes from voltage-mode operation to current-mode operation, using PTAT and CTAT current sources that are inherently less sensitive to device variations. This parameter change eliminates the need for complex trimming processes while maintaining reliable temperature sensing.
Solution Approach 2:
The patent employs a feedback mechanism where the comparator output is fed back to control the current sources, automatically compensating for device variations. This feedback loop ensures reliable temperature sensing without requiring additional trimming processes during manufacturing.
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 approach allows for direct temperature signal processing, reducing circuit complexity and area, and improving accuracy by eliminating sources of variation, thus enhancing the overall performance of temperature sensor circuits.
Implementation Method 1
a first current source is configured to generate a first current whose value is proportional to a temperature
Implementation Method 2
a second current source is configured to generate a second current whose value is complementary to the temperature
Data Source
AI summary
A temperature sensor circuit is disclosed that uses multiple bipolar devices to generate a proportional to absolute temperature (PTAT) current and a complementary to absolute temperature (CTAT) current. A difference in the PTAT and CTAT current is evaluated using a feedback loop of an amplifier circuit which alternatively charges and discharges a capacitor to create a time-varying analog signal. A comparator circuit compares the analog signal to threshold values to generate an output digital signal whose duty cycle varies with temperature.