Using NI LabVIEW and PXI to Reduce Video DAC Testing Time by 97 Percent

Author(s):
Sam Yang - Sunplus Technology Co.

Industry:
Electronics

Products:
PXI-4110, PXI-4071, LabVIEW, PXI-6542, PXI-2576

The Challenge:
Developing a system to quickly and efficiently validate video digital-to-analog converters (DAC).

The Solution:
Using the NI LabVIEW development environment and PXI hardware to create a test platform that reduces test time by 97 percent.

Previously, validation testing for a video DAC took more than 10 working days. This inefficient hardware test model took too much time, and it was difficult for the engineer to quickly identify problems on the electric circuit, and in the time-constrained semiconductor industry, this became a serious problem.

To help resolve this issue, we used the LabVIEW graphical development environment with a combination of digital multimeters, digital I/O devices, and switches to rapidly extract data and reduce test time by 97 percent. By switching the testing approach, we also reduced errors caused by the manual configuration of plugs, which further improves testing efficiency.

The Introduction of Software-Defined Hardware
The objectives of this project included:

• Developing an automated testing system for video DAC systems used in digital electronic household appliances
• Improving the performance of product testing
• Reducing the frequency of repetitive human manipulation by implementing a standardized automated platform.
The entire testing infrastructure was separated into hardware and software elements.

Developing a High-Speed Hardware Architecture
We achieved a significant reduction of test time by replacing the original test environment with NI PXI hardware. In the past, due to the speed limitation of GPIB and digital multimeters it took one second to finish testing voltage. To finish testing an entire channel, it took about 10.5 hrs. With its exceptional efficiency, the NI PXI-4071 digital multimeter reduces the test time of per step voltage to 33 ms. Thus, it now takes less than 20 minutes to finish testing the entire item, resulting in tremendous time savings.

Using the NI PXI-4110 power supply to replace the traditional power supply provides a stable source of voltage for the DAC that can be controlled and minimizes the testing space. Due to the testing requirements, each channel can be switched to two different load resistances for different current value modes: full current (37.5 Ω) and 1/4 current (150 Ω). Previously, we had to switch the electronic current by manually soldering the resistor. For example, to test a chip with four channels we had to change four resistances in one electric current. It was time consuming, and it increased the risk of the pad falling off the printed circuit board.

Building an Intuitive Front Panel Using LabVIEW
We used LabVIEW graphical programming software as the development environment to construct an intuitive front panel interface. The front panel displays the real-time testing status and each block functions according to the following:

• Initial DAC voltage and the reference voltage value to show the level being measured
• Real-time voltage measure taken by the NI PXI-4071 multimeter
• X-Y plots to show the voltage change per digital code
• Ability to automatically change the test mode to show the current pin configuration status of the NI PXI-6542 high-speed digital I/O device
• Manual configuration block testing
• Choice of the files’ directory and format (.txt or .xml)
• Single status measurements with real-time reporting

We developed the new testing platform successfully using NI PXI modules to reduce the testing time from 4,756 s to 138 s. In the competitive electronic industry, time is of the essence and it is imperative to minimize the time frame from R&D to mass production. Therefore, the testing time is heavily weighted in the success of the whole process. The highly efficient automated testing platform generated from the combination of National Instruments software and hardware has greatly reduced the testing time. Our department is now able to produce the most accurate testing numbers within the shortest possible timeframe.

Author Information:
For more information on this Case Study, contact:
Sam Yang
Sunplus Technology Co.

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