A/D Converter Self-Calibration Using Integrated Reference Timing
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Solution Overview
Problem
Existing A/D converters require external measurement devices for calibration due to changes in linearity and offset over time, making it difficult to calibrate multiple converters at remote locations.
Innovation Solution
A self-calibration-function-equipped A/D converter that includes a first reference voltage unit, a second reference voltage unit, an integration unit, a comparator, a calibration control unit, and a conversion control unit, which allows for internal calibration without external devices by generating and integrating reference voltages and measuring integration times to adjust unit voltages and offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If periodic calibration is performed to maintain conversion accuracy over time, then conversion accuracy is maintained, but external measurement devices and manual intervention are required
Solution Approach 1:
The A/D converter performs self-calibration by internally generating reference voltages through its own D/A converter and comparator, eliminating the need for external measurement devices. The calibration control unit automatically executes calibration routines, allowing the device to maintain its own accuracy without external intervention.
Solution Approach 2:
The calibration function is built into the A/D converter structure, with calibration circuits and control logic integrated beforehand. This preliminary preparation enables the device to perform calibration autonomously when needed, rather than requiring external setup each time calibration is required.
2Measurement precision
If a reference measurement device is used for calibration, then calibration accuracy can be achieved, but it is difficult to calibrate multiple A/D converters at remote locations
Solution Approach 1:
Each A/D converter contains its own calibration capability, generating reference voltages internally through its D/A converter. This self-sufficiency allows any number of converters to be calibrated independently at remote locations without requiring transport to a central calibration facility with external measurement equipment.
Solution Approach 2:
The calibration function is integrated into the standard A/D converter structure, making the calibration capability universal across all instances of the device. The same internal mechanisms that perform normal conversion also enable calibration, allowing consistent calibration procedures across multiple devices regardless of location.
3Manufacturing precision
If resistor elements are adjusted to enhance linearity and accuracy, then output accuracy is improved, but adjustment requires external measurement devices
Solution Approach 1:
The A/D converter uses its own internal resources (D/A converter, comparator, and existing circuitry) to perform calibration and verify accuracy. The calibration control unit automatically adjusts resistor elements based on internal measurements, eliminating the need for external measurement devices and complex manual adjustment procedures.
Solution Approach 2:
The calibration function merges the measurement and adjustment capabilities into the existing A/D converter structure. The same comparator and control logic used for normal operation are also employed for calibration, combining multiple functions into the existing circuitry rather than adding separate external calibration equipment.
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
Enables self-calibration without external measurement devices, ensuring high long-term stability and low power consumption, maintaining conversion accuracy over time.
Implementation Method 1
an integration unit that generates an integrated voltage obtained by integrating unit voltages using any one of the first reference voltage, the second reference voltage, and a ground voltage as an initial value during calibration
Implementation Method 2
a comparator that compares the integrated voltage with a threshold voltage and outputs a determination signal
Implementation Method 3
a first reference voltage unit that generates a temperature-compensated first reference voltage
Data Source
AI summary
An A/D converter includes: a first reference voltage unit that generates a temperature-compensated reference voltage; a second reference voltage unit that generates a second reference voltage calibrated with the reference voltage; an integration unit that generates an integrated voltage obtained by integrating unit voltages using any one of the reference voltage, the second reference voltage, and a ground voltage as an initial value during calibration; a comparator that compares the integrated voltage with a threshold voltage and outputs a determination signal; a calibration control unit that measures an integration time until the integrated voltage exceeds the threshold voltage from the initial value during calibration and calibrates the unit voltages and an offset voltage of the comparator; and a conversion control unit that converts an input voltage into a digital value using a conversion integration time which is the integration time when the input voltage is an initial value and the second reference voltage during conversion.