Built-in Test Circuit for High-Speed Analog AC Transfer Characteristic
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Solution Overview
Problem
Testing high-speed analog circuits using external test equipment is inefficient due to the need for high-frequency digitization and post-processing, which increases test time, especially for devices with large gain, and can result in poor signal-to-noise ratios.
Innovation Solution
A built-in test circuit integrated on the same IC die as the device under test, comprising an amplitude detector, differential comparators, and a Boolean logic AND gate, allows for real-time measurement of the AC transfer characteristic without the need for external high-frequency digitization, using differential sinusoidal signals and threshold comparisons to reduce test time and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external test equipment with high-frequency digitizer is used to test AC transfer characteristic, then measurement capability is improved, but test time increases significantly due to post-processing requirements
Solution Approach 1:
The patent extracts the measurement function from external test equipment and implements it within the integrated circuit itself using a built-in test circuit. This allows the AC transfer characteristic to be measured without requiring external high-frequency digitizers and post-processing, thereby eliminating the time penalty associated with external measurement systems.
Solution Approach 2:
The device under test performs its own measurement using an integrated built-in test circuit. The test circuit includes a test signal generator, amplifier, and comparator that work together to measure the AC transfer characteristic internally, eliminating the need for external measurement equipment and its associated time constraints.
2Measurement precision
If attenuated test input signal is used to measure linear gain of high-gain device, then measurement accuracy is improved, but signal-to-noise ratio deteriorates and test time increases
Solution Approach 1:
The patent changes the operating parameters of the measurement system by using a non-attenuated test input signal combined with a switchable gain stage. The gain stage can be configured to provide different amplification levels, allowing the system to measure linear gain without signal attenuation while maintaining adequate signal-to-noise ratio through proper gain selection.
Solution Approach 2:
The patent introduces a switchable gain stage as an intermediary component between the test signal generator and the device under test. This gain stage acts as a mediator that can be configured to provide appropriate signal amplification, eliminating the need for signal attenuation while maintaining measurement accuracy and improving signal-to-noise ratio.
3Measurement precision
If external test equipment is used to measure AC transfer characteristic, then measurement functionality is provided, but device complexity and test setup complexity increase
Solution Approach 1:
The patent merges the measurement functionality into the integrated circuit by integrating a built-in test circuit that includes a test signal generator, amplifier, and comparator. This consolidation eliminates the need for separate external test equipment and reduces overall system complexity while maintaining measurement capability.
Data Source
AI summary
An analog device under test circuit and a built-in test circuit for testing an AC transfer characteristic of the analog device under test are fabricated on an integrated circuit. The built-in test circuit includes an amplitude detector that detects the amplitude of the output signal of the analog device under test. The test time is reduced by sampling in real-time the DC value corresponding to the amplitude of the analog device under test. An additional reduction in the test time is achieved by using comparators with upper and lower limit reference signals and a pass-fail logic test.