Delta-Sigma Integrator RC Calibration Using DC Output Measurement
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Solution Overview
Problem
Existing methods for calibrating the time constant RC in integrated circuits, such as those used in analog/digital converters, suffer from insufficient precision due to inherent inaccuracies in integrated resistance and capacitance, leading to suboptimal filter performance and stability issues, especially in delta-sigma modulators.
Innovation Solution
A method and system for measuring the time constant RC within an integrated circuit using an operational amplifier coupled with resistive and capacitive elements, where a continuous analog input signal is applied to determine the time constant based on output signal measurements, allowing for autocalibration without an additional calibration circuit, thereby improving precision and reducing errors from hardware imperfections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration methods using quartz-driven clocks or voltage comparisons are used, then the time constant RC can be measured, but the measurement precision is insufficient due to hardware imperfections such as operational amplifier offset voltage and comparator errors
Solution Approach 1:
The patent extracts the time constant measurement function from the main signal processing path by using a dedicated calibration mode. The system separates calibration operations from normal operation, allowing precise measurement of RC without interference from operational amplifier offset voltages and comparator errors that affect the main signal path. This extraction enables independent calibration with higher precision.
Solution Approach 2:
The patent introduces an intermediary calibration signal path that uses a known reference voltage and a controlled switching mechanism. This intermediary path allows the system to measure the time constant RC through a separate route that avoids the harmful effects of operational amplifier offsets and comparator errors, thereby improving measurement precision and reliability.
2Measurement precision
If additional calibration circuits are added to improve measurement precision, then time constant calibration accuracy increases, but device complexity and circuit area increase
Solution Approach 1:
The patent makes the existing operational amplifier and comparator circuits multi-functional by enabling them to operate in both normal signal processing mode and calibration mode. The same hardware components perform dual functions: signal processing during normal operation and time constant measurement during calibration. This eliminates the need for separate dedicated calibration circuits, reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The system uses its own existing hardware components (operational amplifier, comparator, switching mechanism) to perform self-calibration of the time constant RC. No external calibration equipment or additional dedicated calibration circuits are required. The system calibrates itself using internal resources, simplifying the overall device architecture while achieving high calibration accuracy.
3Ease of manufacture
If integrated resistance and capacitance values are used directly, then the circuit is simple to manufacture, but the time constant RC precision is insufficient with tolerances of +/â35%
Solution Approach 1:
The patent performs preliminary calibration of the time constant RC during the manufacturing or initialization phase. By measuring and storing the actual RC values of the integrated components before the circuit enters normal operation, the system compensates for manufacturing tolerances. This preliminary action allows the use of standard integrated components with wide tolerances while achieving precise time constant control through pre-characterization.
Solution Approach 2:
The patent changes the operating parameters of the calibration circuit to optimize the measurement of time constant RC. By adjusting the calibration signal frequency, amplitude, or waveform characteristics, the system maximizes the precision of RC measurement despite the inherent tolerances of integrated resistance and capacitance components. This parameter optimization enables accurate calibration without requiring tighter manufacturing tolerances.
Data Source
AI summary
A method and system for measuring a time constant RC of an integrated electronic circuit is provided. This integrated circuit may be made up of a first hardware component and of a second hardware component wherein one of the hardware components is a resistive element and the other is a capacitive element. The first and the second hardware components are connected to an inverting input of an operational amplifier of an integrator of a delta-sigma modulator. A DC voltage is applied to the modulator input. The output signal Qs of the modulator is measured with the aid of an analog/digital converter, and the value of the time constant RC is determined on the basis of at least one measurement of the level of the DC component of the output signal Qs of the modulator carried out with the air of a measurement counter circuit.