http://vtiinstruments.com/CaseStudy/ 1047_CS06_MEMS_d03
Scalable LXI DAQ Solution
for MEMS Transducer Testing
Micro-Electro-Mechanical Systems (MEMS) transducers are important for any electromechanical measurements that need to be made in a small footprint, such as monitoring
pressure on a miniature piece of electronics. MEMS-based sensors are used in critical
automotive, medical and industrial applications worldwide. For example, automobiles can
electronically monitor tire pressure and report it to the driver using this technology.
This company manufactures MEMS pressure transducers, which are pressure sensors
specifically designed to fit into a micro-sized footprint. For this company’s specific
product, the transducers are made for printed circuit boards. As an end-to-end solution,
the integrated circuit provides signal conditioning and digitizes the transducer output. In
some cases, the transducer even applies calibration coefficients to the digitized voltage.
MEMS Transducer Testing:
Why It’s Important
To ensure quality, each transducer is verified for functionality and accuracy. Testing
requires an excitation source (voltage or current) and then a voltage or resistance
measurement to read the transducer output. Verification occurs across a wide
temperature spectrum and should be done in parallel for large batch quantities.
The Challenge:
Cost-Effective, Automated MEMS Testing
In the past, MEMS testing had been a long and arduous task for the customer since it was
mostly a manual process involving benchtop equipment. The company was looking for
an affordable, automated process that would drastically decrease test time and improve
throughput.
The customer initially planned to use a programmable power supply as an excitation
source for all the DUTs being tested in parallel. For a current-based excitation source,
external circuitry would be required to make the conversion from voltage to current, as
well as to ensure a stable, uniform current value from channel to channel.
After considering solutions from two other instrument suppliers, the company approached
VTI Instruments for help.
The Solution:
LXI DAQ System With Increased Test Throughput
After taking the time to fully understand the application, VTI presented the customer with
a DAQ solution that was able to provide an individual excitation source for each DUT in
the system at a reasonable cost per channel. VTI’s analog sources can be programmed to
provide either current or voltage on a per-channel basis.
To meet the customer’s needs, VTI provided several instruments from its EX1200 series
of precision switch, measure and control products: the EX1266, EX1262, EX1200-4128,
EX1200-3164, EX1200-3604 and EX1200-3608. The EX1200 is the highest density
switching platform available and the only LXI Class A subsystem on the market. It
includes a full-featured 6.5 digit DMM, precision analog and digital I/O modules, and an
internal analog expansion bus.
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Scalable LXI DAQ Solution for MEMS Transducer Testing
The scalability of the EX1200 allows the customer to add DMMs at a manageable cost,
which also increases the throughput of the overall system. The competition was unable to
provide comparable solutions that would scale up in size at a reasonable price.
n This system was built to test trays of several chips at once. One source is dedicated
to each chip, which is fed into the (1 X 8) multiplexers. Therefore, the source can be
routed to any of the eight pins and used as either a current or a voltage source. Three
general purpose sources, which feed into the matrix, were needed. For example, some
chips required 5V power and one chip required voltage for its I2C component. All
voltage signals can be routed and managed using the switching matrix.
n The diagram shows two chip styles, each with different pinouts. However, the system
was built to arbitrarily test eight pin chips, regardless of pinout. In any given test, all
the chips will be the same style.
n The sources are all a combination of EX1200-3604 and -3608 DAC cards.
n The design allows DMMs to be added when increased throughput is required.
Due to the success of this DAQ system integration, this MEMS testing company is
considering purchasing more EX1200 instruments for the future. The company may
also use VTI hardware for a new tester in development that will be marketed to other
companies.
About VTI Instruments Corporation
VTI Instruments delivers precision instrumentation for electronic signal distribution, data acquisition, and
monitoring. The company continues to lead in the development of open standards for test and measurement
along with scalable, modular products that maximize performance in a small footprint. With nearly two
decades of experience primarily in the aerospace, defense, and energy and power generation markets, VTI
helps customers maintain a competitive edge and preserve the integrity of their brand.
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