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August 3, 1998
Be wary of "complete" devices
Being a technical trade-press editor, I see lots of new-product announcements. Many of
these announcements tout the product--whether it's an IC, a chip-set, or a board--as
"complete." I've always wondered about that term: complete with respect to what?
After all, a truly complete product would require just an input source, an output port,
and a power supply, with no need for user-supplied passive components, buffers, or input
or output amplifiers. Yet, even the latest and most functionally complex chip sets still
seem to require many auxiliary and support components.
I suppose the definition of complete depends on what the vendor provides. If you are a
GSM-phone chip-set provider, a complete chip set might encompass the core functions, but
those RF input-and-output power amplifiers--ah, well, those might not be within the chip
set's scope. And, if a vendor offers complete motor control, the vendor certainly can't
provide the final drive power amplifier or velocity sensor, because its devices have to
match to the motor specifics.
In comparing design alternatives, you need to be aware of what it will take to provide
a finished design. All those lesser parts affect final cost, board space, debugging time,
power consumption, and manufacturing and purchasing issues. Still, all other things being
equal, you can make a strong technical case for favoring the more complete offering.
But such things rarely are equal. When you use a more complete source, you run the risk
of buying into excess capabilities or operating restrictions. You may be paying for
something you don't need, such as a voltage reference embedded within an A/D or D/A
converter, when you really plan to implement one system-wide, higher accuracy reference.
Or, you may find that the complete approach doesn't let you do something you really need
to do to meet your application requirements. In effect, your hands are tied.
The business perspective is equally important. If you can buy a fairly complete
solution, your competitors can buy one, too. The packaging may be the only thing that
differentiates your product from all the similar ones on the market. That fact should make
any electronic engineer uncomfortable!
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