On Wednesday 14 September 2005 01:36 pm, Dan McMahill wrote:
> > Not all glue logic devices are created equal. There are devices made by
> > different manufacturers that have the same part number that are *not*
> > interchangeable under all conditions. The pinout is the same- Everything
> > appears to be the same when you look at the data sheet until you look at
> > the diagram of the internal logic of how the chip works. In essence, the
> > structure of the internal logic of a given device that is made by
> > multiple manufacturers differs. That is, Unless one manufacturer has
> > granted a license to another manufacturer to make a device using their
> > logic and process. So, tags don't work - They just cover up the problem.
> >
> > Also, this issue goes way beyond glue logic into many other families of
> > devices.
>
> To add to what Marvin said, I have first hand seen where two vendors of
> a particular comparator were not the same because the ESD protection was
> significantly better from one vendor than another. Learned the hard way
> when purchasing "saved some money".
>
> This isn't limited to semiconductors by any stretch. Take an
> electrolytic capacitor of a particular capacitance and voltage rating.
> Now see how many variations in ESR (causes internal heating if you're
> using this in a switching power supply app), quoted lifetime,
> temperature at which that lifetime is quoted at, etc. Of course the
> symbol can always be the same.
>
> What I've seen in at least one large company is the CAD libraries are
> all organized by internal part number anyway. In other words, if you
> want a "1206 size, metal film, 1/8W, 1% 4.99k ohm resistor", you simply
> instantiate a "192837.sym" which you know because you have some silly
> notebook on your desk listing all the common passives you use and you
> have the internal part number database open to search for the
> semiconductors.
It seems to me that a browser should reflect the structure of what
it is browsing - That is, if your interested in being able to navigate the
directory without the browser (ie, the command line). How about
organizing the directories along the lines of something like:
Logic ----> LV ----> 74LV ----> mfg1 ----> pn, pn, pn, pn
| ----> mfg2 ----> pn, pn, pn, pn
| ----> mfg3 ----> pn, pn, pn, pn
|----> ABT ----> 74ABT ----> mfg1 ----> pn, pn, pn, pn
----> mfg2 ----> pn, pn, pn, pn
----> mfg3 ----> pn, pn, pn, pn
Something like the above should work for every type of componet. What
I don't want is a structure that takes an approach of throwing everything
into a particular directory because it's quick and easy (Just think of the
Mandrake distribution approach to putting everything into /usr/bin. What a
mess...) or a parts library that can only be browsed using a parts browser.
Regards
Marvin
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