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From: legg <legg@nospam.magma.ca>
Newsgroups: sci.electronics.design
Subject: Re: Operating temperature derating
Date: Sat, 08 Jun 2024 00:25:25 -0400
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On Fri, 7 Jun 2024 15:16:49 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:

>On 6/7/2024 2:59 PM, legg wrote:
>> On Fri, 7 Jun 2024 12:45:24 -0700, Don Y <blockedofcourse@foo.invalid>
>> wrote:
>> 
>>> On 6/7/2024 6:35 AM, legg wrote:
>>>> Commercial considerations of free enterprise have always pushed
>>>> human behaviour towards banditry, so what can I tell you?
>>>
>>> But banditry would suggest taking advantage of the customer.
>>> This is the opposite; the customer gets *more* performance
>>> than the stated capabilities.
>>>
>>> But, no way to know HOW MUCH more!
>> 
>> What exactly IS your concern?
>
>I want too know how much MORE than the published/unpublished operating
>limits one can reasonably expect from a piece of kit -- given that
>these limits don't seem to TRULY represent "maxima".
>
>We have a general idea of the types of components used in these
>things and realize that their operating limits usually exceed the
>published limits for the composite device -- often by a lot!
>
>This suggests (to me) that the published limits aren't backed by
>"real" engineering or stress testing.  But, rather, likely arise
>from marketing specs... someone making a SWAG as to how customers
>will LIKELY use the devices and not what their actual design limits
>happen to be.
>
>[Given that using ANYTHING beyond its operating limits leaves you
>without a leg to stand on, it would be nice to have some idea as to
>what a reasonable expectation for those limits might be, despite
>the "fluff" on the spec sheet.  E.g., I would be really pressing my
>luck to use something at 80C in that most components would likely
>not be specified at those extremes.  But, 55C for a 50C-specified
>device?  60C?]

Given that you expect to get what's promised when you pay for it, 
outside of banditry, I only expect performance and a reasonable 
service life.

I often kick mysellf in the head when I realize that shortcomings 
in product performance were actually predicted in the written 
specification - that the performance that I was expecting was not 
only outside published spec, but might not be physically 
possible, using current materials and techniques.

RL