Self-Testing DAC Circuit for Fast Pass-Fail Output Verification
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Solution Overview
Problem
Existing digital-to-analog converter (DAC) circuits require manual testing after fabrication, which is time-consuming and costly, as they need to measure the output voltage for each digital value to determine if the circuit operates correctly, and there is no integrated method to detect open-circuits or short-circuits in the switches.
Innovation Solution
A self-testing DAC circuit with a test portion that initiates a test mode, cycles through digital input values, compares the output voltage with a predetermined test voltage, and provides a digital output indicating acceptance or failure, allowing for integrated self-testing and reducing the need for manual measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual testing is performed by measuring output voltage for each digital value, then testing accuracy is improved, but testing time and cost increase
Solution Approach 1:
The DAC circuit performs self-testing by internally comparing its own output voltage against predetermined test voltages for each digital value, eliminating the need for external manual measurement equipment and operators. The circuit autonomously generates test patterns, measures its output, and determines pass/fail status, thereby reducing testing time while maintaining accuracy through integrated comparison circuits.
Solution Approach 2:
The patent introduces comparison circuits as intermediaries that automatically compare the DAC output voltage with predetermined test voltages stored in memory. These comparison circuits serve as mediators between the DAC output and the test result determination, enabling rapid automated testing without manual intervention while preserving measurement precision through systematic voltage comparison.
2Difficulty of detecting and measuring
If manual testing is performed for each digital value, then detection capability is improved, but device complexity increases
Solution Approach 1:
The patent merges the test generation, voltage comparison, and result determination functions into the DAC circuit itself. The comparison circuits, memory for storing test voltages, and control logic are integrated with the DAC, creating a unified self-testing system that maintains high detection capability while reducing overall system complexity by eliminating separate external testing equipment.
Solution Approach 2:
The DAC circuit is designed to perform both its primary conversion function and self-testing function using the same hardware resources. The comparison circuits and memory structures serve multiple purposes within the integrated system, enabling the circuit to detect open-circuits and short-circuits without requiring additional dedicated testing components, thereby maintaining detection capability while minimizing added complexity.
3Reliability
If comprehensive testing of all digital values is performed, then reliability is improved, but productivity decreases
Solution Approach 1:
The self-testing mechanism operates periodically during fabrication by cycling through predetermined digital values and comparing output voltages at regular intervals. This periodic automated testing ensures comprehensive reliability verification of the DAC circuit across its full operating range while maintaining high fabrication throughput by eliminating manual testing bottlenecks and enabling parallel processing of multiple circuits.
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 significantly shortens testing time and reduces fabrication costs by enabling rapid cycling through digital values without measuring output voltage for each input, providing a digital output that indicates circuit acceptance or failure, thus identifying open-circuits or short-circuits.
Implementation Method 1
a comparator to compare a magnitude of the output voltage with a predetermined test voltage
Data Source
AI summary
One embodiment of the invention includes a digital-to-analog converter (DAC) circuit. The DAC circuit includes a DAC portion configured to generate an output voltage having a magnitude that varies based on a plurality of digital values of a digital input signal. The DAC circuit also includes a test portion configured to compare the output voltage with a predetermined test voltage for each of the plurality of digital values of the digital input signal during a test mode. The test portion can provide a digital output signal corresponding to one of acceptance and failure of the DAC circuit.