I was looking at the schematic of a relatively new product's design and saw an IC labeled with the prefix “UCC.” I paused and wondered, “Who's that?” and then I remembered: That prefix belonged to ICs from Unitrode, which was bought by Texas Instruments in 2000. You can still get many of those Unitrode parts from TI, and under their original part numbers.
It's not news that companies come and go. Sometimes they close up and disappear completely, or they are bought out by a competitor. Other times, they merge with a complementary vendor. In most cases, though, their parts live on, and are even used in new designs.
Why would a design engineer use parts like these in new designs, when their “ownership” is, shall we say, a little cloudy? I think it's because designers like to go with parts they have used before. There are several reasons for this: They understand the part reasonably well, they know which layouts work and which don't, they know about the associated passives, they know how to assess and test the part when needed, and they believe know they its idiosyncrasies (and all parts have them).
But there's more to it, from what I've seen. When designing a new product, every team has to decide where to take chances and where to play it safe. Most projects can only deal with “new and risky” in about 10-20 percent of the design; by re-using parts and subsections from previous designs, they can establish bounds on how many areas with unpleasant surprises they'll likely encounter.
It's especially the case when using analog and power parts, where new parts can certainly give you better performance, but older parts are often “good enough” to meet the objectives. Hey, they do the job, they do it well, and they do it without hassle — so why not use them again?
That's one of the many reasons you'll see older parts, which could be retired, still going on new BOMs, often from vendors who no longer are what they were. Fortunately, when companies acquire others (or take on their parts and related IP), they almost always keep the original prefix and part number. This makes a lot of sense, as the part is still inventoried under that designation, and is on various approved vendor lists that purchasing or the contract assembler uses.
Have you ever deliberately used an “older” part that you liked, rather than check for newer, perhaps better ones? Have you ever considered using a part with a prefix that is unusual, but from a credible vendor? Did you wonder how it got there? Are there any vendor names you haven't heard in a long time, but you still occasionally see through their parts — which live on?