For instance, if the limit is the junction temperature, there's some thermal
resistance between the reference junction and the measurement point, so if
the chip is dissipating more, the delta T between limiting point and
measurement point is greater.
and therefore the published max operating temp would be lower.
work hotter or cooler. (and a lot of times, those limits might be
determined empirically... They test a bunch of cases, and that's what gets
published in the data sheet)
no, I believe it's standard practice to characterize individual chips
as they're produced ("binning"), with specific markings (clock, temp range)
to communicate the results.
http://support.amd.com/us/Embedded_TechDocs/43374.pdf
has a number of tables that, for instance, define a thermal profile ("V")
which requires a Tcase max of 64C at 165W (! though there aren't actually
any models listed in the doc rated to dissipate that much). all the profiles
listed have a tcase-max of between 64 and 86C.
if you operate the chip within spec, you should expect the lifespan
to be plenty long (basically indefinite, but let's say 10 years...)
Maybe, maybe not. The chip life generally follows Arrhenius rule (roughly
halving life for 10C rise), but it's hard to know what the "rated" life is,
hmm, I was assuming a lifetime warranty, but indeed, the terms are 3 years.
it would be surprising if you couldn't operate the chip within its thermal
spec, continuously, for 3 years, with low failure rates...
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