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From: legg <legg@nospam.magma.ca>
Newsgroups: sci.electronics.design
Subject: Re: Operating temperature derating
Date: Thu, 06 Jun 2024 13:45:28 -0400
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On Mon, 3 Jun 2024 07:52:58 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:

>Presumably, one should feel comfortable using a device at the
>published operating temperature extremes "forever".
>
>But, what sort of derating likely went into that specification
>in the first place?  Sad another way, how much *beyond* those
>limits might want suspect you could operate the device?

There are two basic limits to operating environment temperatures.

Junction temperature limits are usually proscribed below book 
Tjmax for an agreed mtbf. Sometimes the environmental limits 
can be extended under reduced performance guidelines, without 
exceeding agreed Tj limits.

For a whole product, there's usually other component limiting factors 
that occur first - electrolytic and film capacitors, insulation system
ratings and surface touch restrictions.

Performance is measured with these specified limits in mind.

or not.

RL