Temperature Sensor Linearity via Dynamic DAC Adjustment
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Solution Overview
Problem
Existing temperature sensors face challenges in achieving good linearity between temperature and digital codes over a wide temperature range, leading to poor temperature measurement accuracy due to DAC code-to-temperature non-linearity issues.
Innovation Solution
A temperature sensing circuit that provides a temperature-dependent reference voltage and a compared voltage, with a comparator adjusting DAC codes to ensure equality between the two voltages, establishing a linear relationship between temperatures and DAC codes, thereby improving accuracy and allowing for simple calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DAC based temperature sensing is used, then temperature measurement capability is provided, but linearity between temperature and digital codes deteriorates
Solution Approach 1:
The patent changes the operating parameters of the DAC by introducing temperature-dependent compensation voltages that adjust the DAC code-to-voltage mapping. This dynamically modifies the conversion characteristics to maintain linearity across varying temperature conditions, directly addressing the non-linearity issue in conventional DAC-based temperature sensors
Solution Approach 2:
The patent implements a feedback mechanism where the temperature sensor output is fed back to adjust the DAC reference voltage or coding scheme. This closed-loop approach continuously compensates for non-linearities, ensuring that the digital codes remain linearly proportional to temperature throughout the measurement range
2Measurement precision
If CTAT voltage comparison is used, then temperature sensing is enabled, but temperature measurement accuracy deteriorates due to high temperature coefficient
Solution Approach 1:
The patent applies the counterweight principle by introducing compensation voltages or currents that oppose and cancel out the high temperature coefficient effects of the CTAT voltage. This balancing approach neutralizes the temperature drift, allowing accurate temperature measurement despite the inherent temperature sensitivity of the CTAT voltage
Solution Approach 2:
The patent combines multiple voltage sources with different temperature characteristics (PTAT and CTAT voltages) to create a composite reference voltage system. This composite approach leverages the complementary temperature dependencies to achieve overall temperature stability and improved measurement accuracy
3Measurement precision
If PTAT voltage comparison is used, then temperature sensing is enabled, but temperature measurement accuracy deteriorates due to intrinsic DAC code-to-temperature nonlinearity
Solution Approach 1:
The patent transitions from a static DAC conversion scheme to a dynamic one where the conversion parameters are continuously adjusted based on temperature. This dynamic adaptation allows the system to maintain optimal linearity across the entire temperature range, overcoming the limitations of fixed DAC-based approaches
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 enhances the accuracy of temperature sensing by ensuring a linear relationship between temperatures and DAC codes, facilitating easy identification of corresponding temperatures and codes, and enabling effective temperature regulation in semiconductor devices.
Implementation Method 1
VCTAT depends on temperature as complement to absolute temperature
Implementation Method 2
a comparator compares a PTAT voltage and a CTAT base-emitter voltage
Data Source
AI summary
A thermal sensor includes a comparator having a first and second input nodes. A reference voltage generator is electrically coupled with the first input node. The reference voltage generator is configured to provide a reference voltage that is substantially temperature-independent. A temperature sensing circuit is electrically coupled with the second input node. The temperature sensing circuit is configured to provide a temperature-dependent voltage. The temperature sensing circuit includes a current mirror. A first metal-oxide-semiconductor (MOS) transistor is electrically coupled between the current mirror and ground. A first resistor is electrically coupled with the current mirror. A second MOS transistor is electrically coupled with the first resistor in series. The second MOS transistor and the first resistor are electrically coupled with the first MOS transistor in a parallel fashion.