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A case for not choosing the latest components

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8/17/2010 01:31 PM EDT

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jimcondon
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re: A case for not choosing the latest components
jimcondon   8/17/2010 2:34:09 PM
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Dwight makes an excellent point. In our marketplace, we are often dealing with chips in design or just sampling. This has caused us grief on multiple occasions when the chip hasn't come out on time or even at all. While sometimes it's not possible to avoid this, whenever possible getting chips in production and with second sources at least minimizes the issues and risks to the design.

kdboyce
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re: A case for not choosing the latest components
kdboyce   8/17/2010 8:15:46 PM
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On a past engineering design project I was criticized for using older parts, or shall I say parts that have been in production for several years by more than one source. While perhaps not as elegant if I had used the latest and greatest, the design nevertheless worked just fine, and everyone who had to deal with it understood how the design was put together and could also trouble shoot it and fix it if a failure occurred. That is not always the case using FPGA's, PLD's, and the like - even if the parts are available - unless the design documentation is flawless. However, I do understand OEM's who do want a product currently in design because it may contain a feature which gives their products an edge over competition. Both the OEM and the supplier must completely be open in communication and understand the risks involved and have mitigation plans in place. This kind of situation should not be looked at as only a customer-supplier relationship, but as a partnership where both parties have a major vested interest in the project's success.

ttt3
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re: A case for not choosing the latest components
ttt3   8/17/2010 10:14:34 PM
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I was involved in a project where we had an entire circuit card design completed with a 1000+ pin ASIC (each board actually had two of these parts). The ASIC manufacturer had produced sample chips but nothing in volume. Just before we went to build prototypes, the ASIC vendor decided to discontinue the chip before it hit production. Many man hours of wasted effort in board layout, schematic capture, supporting component selection and procurement, etc. However, we ended up starting over with a different ASIC and the project was successful. Never did know why that vendor did samples but killed the part before it hit production. In general, before I select a particular part for a board design, I want to see actual physical stock of the part at a well known distributor. If there's no stock, the part has almost no chance of making it in my design. I have also been bitten by "vaporware" where a vendor will produce a datasheet but no actual parts. Pericom is one vendor I've seen do this. While this is hard to avoid for large ASICs and CPUs, it's a good rule of thumb for smaller ICs, oscillators, crystals, etc.

Dwight Bues
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re: A case for not choosing the latest components
Dwight Bues   8/18/2010 3:13:28 AM
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Interestingly enough, for much of my career, we didn't have design cycles long enough to build prototypes. Although many designs could trace their ancestry back to previous projects, none were "cut and paste", as it were. Add to that the risk of VVI components and you REALLY wanted to make every design "brain dead" simple....

Dwight Bues
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re: A case for not choosing the latest components
Dwight Bues   8/18/2010 3:39:18 AM
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I once was tasked to build a VME System Controller function on a card. The day before the Preliminary Design Review, I realized that I had not implemented the "System Reset" and "AC Fail" (power-up reset) circuitry. I whacked together a circuit implemented with two one-shots and took a beating at the Design Review, as these components were a key part of the system and needed to be reliable (also their functionality at power-up was likely to be flawed). I found a discrete transistor design that my Boss had done on a board that we had used for a many years, implemented two of them for the two different time constants, and happily went to the Final Design Review. My Boss flew into a rage at the discrete transistor design wanting to know "...what IDIOT designed that???". I had a lot of fun telling him who!!!

old account Frank Eory
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re: A case for not choosing the latest components
old account Frank Eory   8/18/2010 4:48:05 PM
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After all these years, I'm still amazed at how many system problems can be traced back to resets. We really make an effort to emphasize this to our young designers -- reset circuits might be very boring and unlikely to jazz up your resume, but they are one of the most likely reasons for your big multi-core SoC to fail. In the modern era of RTL signoff, it might seem anachronistic to insist on any amount of gate-level SDF annotated simulation, but we still do a certain amount of it -- at least enough to see the thing come out of reset and start behaving normally.

Haldor
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re: A case for not choosing the latest components
Haldor   8/20/2010 6:24:52 PM
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We did an ASIC in that contained an 8051 core. I designed our first product containing this ASIC and discovered that the power on reset function (from the IP vendor) was unreliable. Luckily our system had a second processor and I was able to reset the ASIC from the second processor.

dutchmam
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re: A case for not choosing the latest components
dutchmam   8/20/2010 6:32:53 PM
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This is where a seasoned Component Engineer can save the company a heap of trouble. I have seen this so many times, when some hot-shot design engineer who decides to use a part that has a "preliminary data-sheet" associated with it. You warn them, they get huffy and insist in using that part anyway. Usually (sure, not always) this is followed by a PCN (product chance notice) or discontinuation notice. This is one of the things a good Component Engineer does: Warn you of potential disaster in your choice of parts.

W1PK
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re: A case for not choosing the latest components
W1PK   8/20/2010 7:09:48 PM
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It happens. This is one reason I'm very reluctant to design in a component with a production history of less than 5 years. If it's in stock from multiple sources at one of the small-quantity distributors like Digi-Key or Mouser, that gives me a warm feeling too. There are a few manufacturers you really have to watch out for, who will keep a part in production just long enough for you to get through qualifying it, checking out the prototypes, and delivering a pilot run, and then cancelling it when you try to place high-volume production orders. For some markets, such as military aircraft and nuclear power plants, I woudn't dare even consider a sole-source ASIC; with production lives of 10 to 15 years, service lives of 25 to 50 years, and statutory prohibitions against design changes without extensive and expensive requalification, discrete transistor designs are sometimes the only safe option. All hail the 2N2369 and its SMT cousins.

Jerrysc
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re: A case for not choosing the latest components
Jerrysc   8/20/2010 8:24:53 PM
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Some things never change! It is SOP for Marketing to issue product releases for instruments, components, or software that does not exist to one degree or another (but is in the realm of possibility) in order to see if there is enough interest to justify persuing the development or production of same. And if the product is ever successfully developed it wont be in production for long if it is not an economic success.

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