ADC-DAC Feedback Circuit for Faster Static Parameter Testing
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Solution Overview
Problem
Existing test circuits for analog-to-digital converters (ADCs) require long test times due to complex and time-consuming methods for calculating static parameters, such as integral nonlinearity and gain error, because they rely on statistical methods like the linear staircase histogram method which need numerous sampling points.
Innovation Solution
A conversion circuit that forms a test loop between a digital-to-analog converter (DAC) and an ADC, using a comparing unit to adjust test codes and collect voltage values within a preset error range, allowing for quick locking of a test code set and reducing test time by using a one-to-one mapping method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If statistical methods like linear staircase histogram method are used to test ADC static parameters, then measurement precision can be improved, but test time increases significantly
Solution Approach 1:
A DAC (digital-to-analog converter) is introduced as an intermediary component to form a closed-loop test system. The DAC converts digital test codes to analog voltages that are fed back to the ADC input, enabling direct comparison between input and output codes. This intermediary allows the system to obtain accurate static parameters (INL, DNL, gain error) through direct measurement rather than statistical sampling, dramatically reducing test time while maintaining precision
Solution Approach 2:
The patent implements a feedback mechanism where the ADC output codes are compared with the original input test codes, and the difference (error) is fed back to adjust subsequent measurements. The comparing unit calculates the difference between input and output codes, and this feedback enables iterative refinement of measurements, allowing rapid convergence to accurate static parameter values without requiring extensive sampling
2Measurement precision
If multi-point sampling methods are used to ensure sufficient sampling points for accurate test results, then measurement precision is improved, but device complexity and test time increase
Solution Approach 1:
The DAC serves as a mediating device that simplifies the test circuit architecture. Instead of requiring complex multi-point sampling circuits and external test equipment, the DAC creates a direct feedback path from ADC output to input, enabling accurate measurements with a simpler, more integrated circuit design
Solution Approach 2:
The test system performs self-testing by using its own internal DAC to generate the feedback signal. The ADC under test effectively tests itself through the closed-loop feedback mechanism, eliminating the need for external complex test equipment and multiple sampling points, thereby reducing overall device complexity
Data Source
AI summary
The present invention provides a conversion circuit including: an inputting unit, a DAC connected to the inputting unit, an ADC connected to an output end of the DAC, and a comparing unit connected to an output end of the ADC. The comparing unit compares a test code set output by the ADC with a second standard test code set, and if the comparison result is in a preset error range, notify a test data collecting unit; otherwise, output the comparison result to a correcting unit. The correcting unit obtains a complementary code set according to the comparison result, and output the complementary code set to the inputting unit, so that the inputting unit updates the standard test code set according to the complementary code set and obtains the updated first standard test code set. The test data collecting unit obtains a voltage value of an input end of the ADC.