Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: KevinJ93 Newsgroups: sci.electronics.design Subject: Re: Operating temperature derating Date: Sat, 8 Jun 2024 12:03:49 -0700 Organization: A noiseless patient Spider Lines: 75 Message-ID: References: <11n76jpt2qpaq49a6ka0qd8a82o8231o05@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Sat, 08 Jun 2024 21:03:50 +0200 (CEST) Injection-Info: dont-email.me; posting-host="a2af6c3cc7fd15480ecd71a0fae9173c"; logging-data="2882696"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+gdLmRrgMvmzDniHGyiFsP" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:MoxNTE12NMjTZ3jHTj6bM/Ay6so= Content-Language: en-US In-Reply-To: Bytes: 4783 On 6/8/24 4:17 AM, Don Y wrote: > On 6/7/2024 9:25 PM, legg wrote: >>> [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. > > But performance is only formally defined within the "operating conditions". > And, many bits of consumer kit don't even specify these! > >> 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. > > Would you expect a cell phone to operate in the same nominal environments > that a human being would encounter in their normal living?  If it FAILED > to operate "above 93F" (which is likely most of the lower 48, at some > portion of the day, lately), you'd likely be looking for another device > as you would always have to be in an air conditioned environment to make > that guarantee. I used to be in the iPhone design team. At the time we used a 40 deg C as the maximum ambient temperature. As part of the development we would run a "thermal virus" software to cause the CPU to dissipate an approximation for the maximum possible. Under those conditions the internal temperature could get to the 70 deg C region. If excessive temperatures were reached the CPU would be throttled to avoid damage. I was working on the display/touch hardware; LCD displays stop working at about 75 deg C (they just turn black). Since the display was within a couple mm of the CPU there was not margin. Under less stressed conditions the internal temperature was much lower. I suspect that the battery is probably the most sensitive item for storage temperature while not operating, especially if fully charged. kw > [And, if *storage* above 113 was contraindicated, how many could leave > it in an unattended/garaged car?  You KNOW that you can't store *ice* > above 0C and, thus, don't!] > > So, what value writing those limits on the formal product specification? > Obviously (as we haven't seen class-action lawsuits from folks claiming > their thousand dollar phones don't work in the Summer months) the devices > work beyond their stated operational limits. > > Is the limit published solely to give the manufacturer a legal "out" > if large numbers of units suddenly DO start failing?  While that may avoid > a lawsuit, today, how likely would it be to endear future purchasers to > a product if such a constraint became well-known? > > Said another way, why not just *say* "25C" and hope customers are just > as oblivious of the actual declaration? > > *Or*, say 42.1C after a careful analysis of the design and its actual > operating temperature limits? > > [I just don't see value in these numbers as they stand, currently] >