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From: KevinJ93 <kevin_es@whitedigs.com>
Newsgroups: sci.electronics.design
Subject: Re: Operating temperature derating
Date: Thu, 13 Jun 2024 12:42:47 -0700
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On 6/12/24 12:26 PM, Don Y wrote:
<...>
> It's been above 100F (38C) for 16 days, already.  People are still working
> their normal outdoor jobs, looking at cars on dealer lots, walking 100 
> yards
> across uncovered parking lots to gain entry to stores, etc.
> 
> Are phones NOT expected to work in these environments?  (Gee, I wanted to
> telephone emergency services to get help for my buddy who collapsed in
> the heat but it was too hot for my phone to make the call)

The phones may not stop working but may not meet performance 
specifications. For example applications may not work as fast as at 
lower temperatures.

I've never heard of lower level software being compromised at high 
temperatures so basic phone calls would be ok but action video games 
would run slower.

The ASICs I worked on had a -25C to +75C operating range. When the CPU 
was idle the phone would be too hot to hold if the internals were at 75C.

> We expect cars to continue to operate in those temperatures.  What's the
> criteria that we use to determine what should and shouldn't be expected
> to remain operational?

Automotive devices that expect to be in the engine compartment are 
designed for -40C to +125C or +150C.

kw
<...>