Capacitor-Based Temperature Sensor Circuit
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Solution Overview
Problem
Bipolar-based temperature sensors in integrated circuits face accuracy issues due to increased technology scaling, requiring continuous bias current and being sensitive to process spread, which decreases their accuracy.
Innovation Solution
The use of capacitors, specifically fringe and plate capacitors with different temperature sensitivities, to measure temperature by determining the capacitance ratio through a capacitance-to-digital converter, eliminating the need for continuous bias current and reducing error sources, and achieving high resolution without a large dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bipolar-based temperature sensors are used in integrated circuits, then temperature measurement function is provided, but accuracy decreases due to technology scaling and process spread sensitivity
Solution Approach 1:
The patent replaces bipolar transistor-based temperature sensing with a capacitor-based sensing mechanism. Instead of using bipolar transistors that are sensitive to process variations and require continuous bias current, the invention uses capacitors whose capacitance values change with temperature, eliminating the need for complex bias circuits and reducing sensitivity to process spread while maintaining measurement accuracy.
Solution Approach 2:
The patent utilizes the temperature-dependent capacitance parameter of capacitors to achieve accurate temperature measurement. By measuring changes in capacitance values of reference and measurement capacitors as temperature varies, the system achieves high accuracy without being affected by process spread, as capacitor parameters are more stable across manufacturing variations compared to bipolar transistor parameters.
2Measurement precision
If bipolar-based temperature sensors are used, then temperature measurement is achieved, but continuous bias current is required increasing power consumption
Solution Approach 1:
The patent employs periodic sampling of capacitor voltages to determine temperature. Instead of requiring continuous bias current to maintain sensor operation, the system periodically charges capacitors based on their temperature-dependent capacitance values and samples the resulting voltages. This periodic operation eliminates continuous power consumption while maintaining accurate temperature measurement capability.
3Measurement precision
If high resolution temperature measurement is achieved with capacitor-based sensing, then measurement precision improves, but circuit complexity increases
Solution Approach 1:
The patent uses a single operational amplifier to perform multiple functions: charging both the reference capacitor and measurement capacitor, and serving as the input amplifier for the successive approximation register (SAR) analog-to-digital converter. This multi-functionality reduces the overall number of components and circuit blocks required, achieving high-resolution temperature measurement without proportionally increasing circuit complexity.
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 provides accurate temperature measurement independent of voltage, current, or frequency references, with increased sensitivity and reduced error, effectively addressing the limitations of bipolar transistor-based sensors.
Implementation Method 1
a first capacitor, connected between the input and output terminals, and having a capacitance decreasing according to temperature; and a second capacitor, connected between the input terminal and the terminal at the reference potential, and having a capacitance increasing along with temperature
Data Source
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AI summary
Disclosed is an integrated circuit temperature sensor including a first capacitor having a first capacitance relative to a temperature, a second capacitor a second capacitance relative to the temperature, and a controller configured to determine a ratio of the first capacitance to the second capacitance in order to determine a temperature of a region of the integrated circuit.