Self-Referenced Temperature Converter for ADC Gain Error Cancellation
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Solution Overview
Problem
Conventional self-referenced temperature-to-digital converters in system-on-chip (SoC) face errors due to ADC gain variations, which are not adequately corrected by one-point temperature trim techniques, leading to inaccuracies in digital temperature representation.
Innovation Solution
A temperature-to-digital converter design that utilizes first and second complementary-to-absolute-temperature (CTAT) voltages generated by a temperature sensor circuit as reference signals for the ADC during different conversion cycles, eliminating the need for an external reference signal generator and ensuring the temperature output is independent of ADC gain errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bandgap circuit generates the reference signal for the ADC, then the temperature-to-digital converter can operate, but an error in the bandgap circuit introduces error in the digital representation of temperature
Solution Approach 1:
The patent extracts the reference signal generation function from the bandgap circuit and relocates it to the temperature sensor circuit itself. The temperature sensor circuit generates both the temperature sensing signal and the reference signal, eliminating the harmful influence of bandgap circuit errors on temperature measurement accuracy.
Solution Approach 2:
The temperature sensor circuit serves itself by generating the reference signal needed for ADC operation. This self-referenced approach allows the temperature sensor circuit to provide its own reference signal, making the system independent of external bandgap circuits and their associated errors.
2Adaptability or versatility
If a self-referenced temperature-to-digital converter uses internal reference signal, then the converter operates independently, but ADC gain error due to process variation and device mismatch remains uncorrected
Solution Approach 1:
The patent changes the operating parameters of the ADC by using different reference voltages during different conversion cycles. By switching between first and second reference voltages generated by the temperature sensor circuit, the system measures the ADC gain error and compensates for it through digital processing, thereby maintaining measurement precision while preserving independence from external reference circuits.
3Manufacturing precision
If one-point temperature trim technique is used, then the self-referenced converter can be calibrated, but it fails to correct ADC gain error
Solution Approach 1:
The patent implements periodic action by performing multiple conversion cycles with alternating reference voltages. This periodic switching between first and second reference voltages enables the system to measure and compensate for ADC gain error dynamically, going beyond the static one-point trim approach and achieving continuous correction of gain errors.
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 design enhances the accuracy of temperature measurement by eliminating ADC gain errors and eliminating the requirement for an external reference signal generator, resulting in improved accuracy compared to conventional converters.
Implementation Method 1
The temperature sensor circuit is configured to sense an absolute temperature associated with the SoC, and generate first and second complementary-to-absolute-temperature (CTAT) voltages based on the sensed absolute temperature
Data Source
AI summary
A temperature-to-digital converter includes a temperature sensor circuit, an analog-to-digital converter (ADC), and a digital processing circuit. The temperature sensor circuit is configured to generate first and second complementary-to-absolute-temperature (CTAT) voltages based on a sensed absolute temperature. The ADC is configured to receive the first and second CTAT voltages. Further, during first and second conversion cycles of the ADC, the ADC is configured to receive the first and second CTAT voltages, and generate first and second digital voltages, respectively. The first and second digital voltages are generated based on the first and second CTAT voltages, respectively, and a difference between the first and second CTAT voltages. The digital processing circuit is configured to generate, based on the first and second digital voltages, a temperature output voltage that is independent of a gain of the ADC and a digital representation of the absolute temperature.