Delta-Sigma Converter Self-Test Using a Digital Reference Modulator
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Solution Overview
Problem
Delta-sigma data converters require complex and costly test equipment due to high resolution and oversampling demands, leading to lengthy test times and high unit costs, especially under series conditions, with existing self-test methods relying heavily on software evaluation and hardware-intensive setups.
Innovation Solution
A hardware-based, on-chip self-test method for delta-sigma data converters generates a test signal internally with minimal word length, using a digital delta-sigma reference modulator to emulate the analog modulator's transmission function, allowing for accurate testing of both analog and digital components with minimal additional circuitry complexity and low silicon area requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external test devices are used for delta-sigma converters, then measurement precision can be achieved, but device complexity and cost increase
Solution Approach 1:
The patent implements a self-test mechanism where the delta-sigma converter tests itself using an integrated digital reference modulator and test signal generator. The converter's own digital output is fed back through a digital-to-analog converter and compared with the reference modulator output, eliminating the need for external test equipment and achieving both high measurement precision and reduced device complexity.
2Measurement precision
If high resolution and oversampling are used in delta-sigma converters, then measurement precision improves, but test time increases
Solution Approach 1:
The patent generates test signals internally before actual conversion operations using a dedicated test signal generator and digital reference modulator. By preparing test signals and reference outputs in advance through the self-test path, the converter can immediately begin accurate high-resolution testing without waiting for external signal generation, thus maintaining measurement precision while reducing test time.
3Productivity
If internal test devices are used to minimize test times, then productivity improves, but device complexity increases
Solution Approach 1:
The patent designs the digital reference modulator and test signal generator to serve dual purposes: they function as normal conversion components during operational mode and as self-test components during testing mode. The digital-to-analog converter and comparator are used for both signal conversion and test signal comparison, eliminating dedicated test hardware and achieving high productivity without increasing device complexity.
4Device complexity
If hardware-based self-test is implemented on-chip, then device complexity is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent creates a digital copy of the analog delta-sigma modulator's transfer function through the digital reference modulator. This digital model accurately replicates the analog converter's behavior without requiring physical analog components, thereby reducing manufacturing precision requirements while maintaining test accuracy. The digital reference serves as an idealized model that can be precisely implemented in standard digital logic.
Data Source
Figure 1~3
Figure 4
AI summary
The arrangement (1) has an analog delta sigma modulator (3) for receiving an analog input signal (S1) and outputting a digital data stream signal (S2). A digital filter device (6) for receives the stream signal and outputs a digital output signal (S4). A digital reference device (8) is provided for receiving a test signal (S5) and outputting a digital reference data stream signal (S8). A signal receiving device (5, 13) is provided for receiving the stream signals and for outputting the stream signals to a digital filter device. An independent claim is also included for a method for testing a delta sigma data converter.