ADC Reference Resistor Thermal Coupling for Temperature Compensation
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Solution Overview
Problem
Temperature-dependent signals in analog-to-digital converters can lead to inaccurate measurements due to significant temperature coefficients in metal shunt resistors, which are challenging to manage in integrated circuits where pure metals like aluminum, copper, and gold are used for metallization layers.
Innovation Solution
A circuit arrangement featuring a first resistor and a second resistor, thermally coupled and with the same temperature dependency, where the analog-to-digital converter receives a voltage from the first resistor as the signal to be digitized and a reference voltage from the second resistor, ensuring temperature-independent or reduced temperature dependency in the digital signal by matching the temperature dependencies of both resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If metal shunt resistors are used for current sensing, then the voltage drop can be measured and processed in current control circuits, but the significant temperature coefficient of the resistors causes signal changes that prevent precise measurement
Solution Approach 1:
The patent converts the harmful temperature-dependent signal change into a useful reference signal. By measuring the voltage drop across a second resistor (Rref) that experiences the same temperature effects as the shunt resistor, the temperature-induced changes are captured and used as a reference voltage to compensate for the shunt resistor's temperature coefficient, thereby eliminating measurement errors.
Solution Approach 2:
The patent changes the parameter of the reference voltage to match the temperature dependency of the shunt resistor voltage. By selecting a reference resistor with similar temperature characteristics and adjusting its value, the reference voltage dynamically adapts to temperature changes, allowing the analog-to-digital converter to maintain accurate measurements across varying temperatures.
2Stability of the object's composition
If alloys with zero temperature coefficient are used, then temperature stability is improved, but they cannot be processed in integrated circuits where mainly pure metals are processed
Solution Approach 1:
The patent uses resistors made from the same material (pure metal) and processed through the same fabrication steps as the rest of the integrated circuit. This ensures homogeneity in material properties and processing conditions, allowing both the shunt resistor and reference resistor to exhibit matching temperature coefficients while maintaining compatibility with standard IC manufacturing processes.
Solution Approach 2:
Instead of changing the material composition to achieve zero temperature coefficient, the patent changes the resistance value parameter of the reference resistor to create a reference voltage that matches the temperature dependency of the shunt resistor voltage, achieving temperature stability through parameter matching rather than material substitution.
3Measurement precision
If a reference voltage with matching temperature dependency is used, then temperature-induced errors in digitization are reduced, but additional circuit components are required
Solution Approach 1:
The patent makes the second resistor serve multiple functions: it acts as a reference element for temperature compensation, provides a reference voltage for the analog-to-digital converter, and establishes a thermal reference point. This multi-functionality reduces the need for separate compensation circuits while maintaining measurement accuracy.
Solution Approach 2:
The patent merges the reference voltage generation function with the temperature compensation function by using the same resistor (Rref) for both purposes. The voltage drop across this single component simultaneously provides the reference voltage needed for ADC operation and the temperature reference needed for error compensation, eliminating the need for separate reference voltage sources and temperature sensing elements.
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 precise and accurate current measurement over a wide temperature range, reducing temperature-induced errors in digital signal conversion, with the resistors maintaining similar temperature coefficients and resistance changes, thus enhancing measurement accuracy.
Implementation Method 1
The second resistor may be thermally coupled to the first resistor
Data Source
AI summary
Circuit arrangement, including a first resistor, a second resistor, a current source and an analog-to-digital converter. The second resistor is thermally coupled to the first resistor. The current source is coupled to the second resistor. The analog-to-digital converter is configured to receive a first voltage measured via the first resistor as a voltage to be digitized, and is configured to receive a second voltage measured via the second resistor as a reference voltage of the analog-to-digital converter.