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... or Are They Nourishing You With Some Food for Thought About Functional Testing?By Jim Pennington |
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Test
Engineers may be finding it more and more difficult to keep up with the
growing and changing demands created by the never ending craze for
"High(er) Tech" power supplies.
I suspect that to the volume manufacturers of power supplies, the
battle seems unending. There
is, of course, the always-present demand for greater IC integration,
involving higher component and power density.
Notwithstanding
these expected and ongoing developments with product design and
performance requirements, there's a fairly new "trick" available
for helping engineers to better accomplish these goals.
The "trick" is to make power supplies that
"talk" as well as "listen".
Communication "enhancements" enable the power supply to
assume more responsibility for monitoring and governing its own
"health". As
Applications Engineering Manager for Autotest Company, I see a lot of new
stuff - and over the years have witnessed the migration of many new
technologies into the world of power supplies.
Our Functional ATE systems have always required specialized Unit
Under Test
(UUT) communications. These needs have been addressed with a variety of
solutions involving protocols, busses, and advanced levels of component
integration and complexity. For
some high tech Department of Defense (DOD) products, we employed what have
become now proven and accepted solutions such as RS232, RS 485, IEEE 802.3
Ethernet, IEEE 488, MIL 1553, I2C, and many others.
These technologies can simply read a serial number from a register
or actually direct the Power Supply through a complete routine of
calibration and internal verification.
In such cases, the ATE's hardware or equipment responsibilities may
be simple, but the communication process, coordination and test sequencing
can be quite complex. Along
with the continuing trend for making the power supplies more
technologically capable, powerful, versatile and complex there's a rapidly
expanding area of expansion in the field of self-diagnostics and
maintenance. We are
also seeing more and more the use of processors in power supplies ... to
make them more versatile and flexible for diverse applications.
A typical application is with power supplies that are employed as
sub-systems of a more complex DOD product.
These power supplies are often asked to provide much more than just
delivering system power. They
are often integrated and designed to monitor, react and respond to
variable and changing requirements of a much more complex system. At
Autotest, we first addressed these
more complex phenomena with the introduction of our UPS ATE.
The Uninterruptible
Power
Supply (UPS), by design, has a responsibility to communicate with
the computer to which it is delivering backup power.
UPS manufacturers, taking advantage of the need for UPSs to have
communication and processing ability decided to let the processor do other
things as well, like calibrate output parameters and provide functional
controls for supporting them. Built
In Test
(BIT) functionality is
becoming more common with power supplies, making them capable of being
programmed to sequence through an internally controlled test process and
to report the results. With
the integration of a processor and a bi-directional, software-controlled
communication bus to manage this process, significant additional
diagnostics and information can be provided. The
latest communication trend in communications for commercial power supplies
is in the application of the IIC
Bus (Inter-Integrated Circuit), or I2C as it has come
to be called. The I2C
Bus is an essentially a two-wire, low to medium speed, communication bus
developed by Philips Semiconductors in the early 1980s.
It was created to provide a low-cost chip-to-chip communication
links for such things as volume and contrast controls in radios and
televisions. Over the past two decades, the I2C
has expanded its communications role to include power supplies. So
how do Power Supply ATE manufacturers, such as Autotest,
address the changing needs of the Test Engineer? Communication has always
been an integral part of Autotest's ATEs.
We use IEEE 488 extensively to control instrumentation, making
communication integral with all our systems.
Our open-ended software and language simplifies development of
Windows supported communication as an inherent function of test programs
for the UUT.
Perhaps our greatest challenge has been in developing the language
library to simplify the process of building flexible and comprehensive
routines into tests. The I2C
posed a challenge in that regard. A
commercially available PC bus controller, however, provided a simple
solution for adapting the I2C
to developing hardware and software integration for controlling
communication as a part of testing the power supply.
Our APG for
WindowsTM software, implementing and
integrating new protocols and busses, has provided test engineers with an
automated test programming and system control environment tailored to the
needs of most any Power Supply. It
allows a Test Engineer to design simple solutions for complex routines for
engaging a power supply to whatever type of interaction may be required. In essence, the marriage between power supplies and functional testing is a longstanding and always developing relationship. To coin a proven metaphor, "the key to any good marriage is communication."
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