DAC Built-In Self-Test for Dynamic Output Transition Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for testing high fidelity audio output devices, such as DACs, require external equipment and cannot effectively assess dynamic behavior, making them impractical for compact on-chip solutions and limiting the ability to test essential dynamic characteristics.
Innovation Solution
A method using digital control signals to produce desired analogue outputs, such as fixed amplitude sine waves, and determining the duration of fixed voltage segments to assess DAC performance, implemented with simple components like comparators and digital signal processors, allowing for a fully or partially built-in self-test solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If external test equipment with physical test-heads is used to test DACs, then measurement precision can be achieved, but device complexity and cost increase, and the solution is not compact for on-chip integration
Solution Approach 1:
The invention extracts only the essential measurement function from complex external test equipment. Instead of using full-featured external DAC test systems, the patent implements a minimal test circuit that measures only the critical parameter (output voltage) using a simple voltage divider network and comparator, eliminating unnecessary complexity while maintaining measurement capability
Solution Approach 2:
The invention creates a simplified copy of the DAC output measurement function that can be implemented on-chip. Rather than copying the entire external test system, it replicates only the essential voltage sensing capability using scaled-down resistor dividers and level-shifted comparators that mimic the measurement principle of external equipment in a compact form
2Ease of operation
If static test methods are used to test DACs, then simple measurement procedures can be implemented, but dynamic behavior cannot be assessed
Solution Approach 1:
The invention transitions from static to dynamic testing by continuously monitoring the DAC output voltage during code transitions. The test circuit captures the transient response as the DAC output changes from one code to another, measuring parameters such as settling time and overshoot that reveal dynamic behavior, while maintaining relatively simple measurement procedures
Solution Approach 2:
The invention employs periodic code transitions to stimulate dynamic response. By systematically cycling through DAC codes in a predetermined sequence and measuring the output response at each transition, the test method periodically excites the DAC to reveal dynamic characteristics such as linearity, settling behavior, and transient distortion
3Measurement precision
If higher performance ADCs and conventional signal processing are used to test audio DACs, then measurement accuracy improves, but the solution becomes impractical for compact on-chip implementation
Solution Approach 1:
The invention replaces expensive, high-performance ADCs with a simpler, lower-performance voltage comparator that performs the essential measurement function. The comparator provides sufficient accuracy for DAC testing without requiring the high resolution and complex signal processing capabilities of premium ADCs, enabling compact on-chip integration while maintaining adequate measurement precision
Solution Approach 2:
The invention changes the measurement parameters from high-resolution voltage sampling requiring sophisticated ADCs to threshold-based voltage detection using comparators. By measuring voltage levels relative to reference thresholds rather than capturing absolute voltage values with high precision, the system achieves adequate measurement accuracy with simpler components suitable for on-chip implementation
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
This approach provides a cost-effective and compact solution for testing DACs by measuring the time taken for the output to move between fixed voltages, effectively assessing performance and identifying signal non-idealities, even in the presence of noise, and correcting these in the frequency domain.
Implementation Method 1
The DAC output and Va are connected to the inputs of a comparator, such that when the DAC input is changed back to Ca the output rises towards Va, tripping the comparator
Data Source
AI summary
A method for testing a DAC including controlling the DAC digitally to cause it to produce a known desired analog output, for example a fixed amplitude sine wave; determining the duration of fixed voltage segments of the actual output of the DAC and using the duration of the fixed voltage segments to assess or determine performance of the DAC.