Using NI LabVIEW and PXI Modular Instruments for Automated Chip Characterization and Validation

Author(s):
Riemer Grootjans - Electronics and Informatics, Laboratorium voor Micro-en Fotonelektronica, Vriji Universiteit Brussel, Belgium
Daniel van Nieuwenhove - Electronics and Informatics, Laboratorium voor Micro-en Fotonelektronica, Vrije Universiteit Brussel, Belgium
Ward van der Tempel - Electronics and Informatics, Laboratorium voor Micro-en Fotonelektronica, Vrije Universiteit Brussel, Belgium

Industry:
Research, University/Education, Semiconductor

Products:
LabVIEW, PXI/CompactPCI,

The Challenge:
Developing a flexible test system to automatically characterize an integrated circuit under varying conditions.

The Solution:
Using National Instruments LabVIEW and PXI modular instruments to synchronize different instruments and implement a very tight timing and triggering scheme.

The Vrije Universiteit Brussel (VUB) has more than 9,000 students and offers 129 study courses. We have more than 150 research teams working on our two campuses, making VUB one of the biggest centers of knowledge in the capital of Europe.

Chip Testing

One of these research groups, Laboratorium voor Micro-en Fotoelektronica (LAMI), is developing a high-resolution 3D camera system. The system consists of an LED array, a lens system, and a complementary metal-oxide semiconductor (CMOS) integrated circuit (IC). The LED array transmits a modulated signal that is reflected by objects around it. Through the lens, the modulated ray reaches the chip with a variable time (phase) delay based on the modulated light wave’s time-of-flight. The same modulation signal feeds the IC itself, together with 90-, 180- and 270-degree phase-shifted signals. The IC measures the light intensity at each of these phases and outputs the resulting integrated signal on each of its four outputs. These outputs are connected to two synchronized oscilloscopes/digitizers to measure the phase delay in the modulated time-of-flight signal.

The IC is a key part of the system. We are testing various generations and types of ICs, all of which have different configuration parameters, including sensitivity, accuracy, resolution, and external influences.

Mixed-Signal Chip Characterization

The NI PXI system contains a mix of digital and analog instruments to control the LED array, as well as the IC under test, and measure the response. At the beginning of the program, the National Instruments PXI-5404 100 MHz frequency generator triggers and synchronizes each of the PXI devices and provides a common base clock. An NI PXI-5421 100 MS/s arbitrary waveform generator provides the modulated waveform to the LED array. An NI PXI-6552 high-speed digital I/O module outputs the same modulated digital pattern to the chip with a pre-set phase delay. This digital pattern is output on four digital lines, each with a 90-degree phase delay. We use a second synchronized PXI-6552 to control the timing and synchronization of the chip, sample and hold, pixel select, and chip reset signals. We had to use a second PXI-6552 for this because the logical voltage level of the digital modulation signal is different from the chip control signals. The PXI-6552 provides flexible control over the logical voltage levels, though this setting applies to all ports on the board.

The circuitry for each pixel on the IC accumulates the amount of light for every 90 degree phase shift of the input signal and provides this accumulated signal to four separate analog outputs. Two synchronized, simultaneously sampling NI PXI-5122 digitizers, each sampling two channels, acquire the analog signals. Using this approach, we can obtain the phase or I/Q signal of the modulated signal directly from the four axes of the polar diagram. We use an NI PXI-7831R reconfigurable FPGA board to set some of the DC levels required by the chip. In future setups, we plan to implement part of the prototyping and controlling of the IC in the FPGA as well.

The system software is written in National Instruments LabVIEW, which provides an easy-to-use graphical user interface that lets us easily adapt our parameters. We implemented methods to run our tests at night so we can sweep several parameters, such as modulation frequency and phase delay, and measure their influences. We have already used the system several times for a complete semiconductor test.

Advantages of the Test System

The main advantage of our test system is the integration of the analog and digital instruments into one system. The PXI system provides very tight control over timing and minimizes the influence of jitter, providing a much better solution than if we were using separate stand-alone instruments. With NI LabVIEW, we were able to quickly create a system with these timing and triggering features. Another advantage is the flexibility we were able to build in using LabVIEW, as each chip’s control requirements differ slightly.

Conclusion and Future Work

Over the next few months, we will be fully testing new ICs and extending the program with new features, such as artificial intelligence to automatically sweep the parameters to reach an optimum performance for the chip under test. We also have to make the external parameters, such as the background light and the distance to an object, adjustable through the LabVIEW interface.

For more information, contact:
Riemer Grootjans
rgrootja@etro.vub.ac.be

Ward van der Tempel
wvdtemp@etro.vub.ac.be

Daniël van Nieuwenhove
davnieuw@vub.ac.be

VUB
Dept. ETRO/LAMI
Pleinlaan 2
B-1050 Brussels
Belgium

Tel: +32 (0) 2 629 29 82
Web: http://www.etro.vub.ac.be/

 

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