Path: ...!2.eu.feeder.erje.net!3.eu.feeder.erje.net!feeder.erje.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: legg Newsgroups: sci.electronics.design Subject: Re: Operating temperature derating Date: Sun, 09 Jun 2024 01:36:43 -0400 Organization: A noiseless patient Spider Lines: 121 Message-ID: <1iea6jlt7t26l8g15gbjotn88v1c96mpsv@4ax.com> References: <7kq86jlms50jove9ck21gu94nvkftpe3q9@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Date: Sun, 09 Jun 2024 07:34:54 +0200 (CEST) Injection-Info: dont-email.me; posting-host="0e07c63846037a0cbd979bc7bec9d740"; logging-data="3409715"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/9kUBlJSCbBUp+o8ndl3MN" Cancel-Lock: sha1:qUf9mEWUI19bJN0C6txEAuC+Wpc= X-Newsreader: Forte Agent 4.2/32.1118 Bytes: 6383 On Sat, 08 Jun 2024 07:40:50 -0700, john larkin wrote: >On Sat, 08 Jun 2024 00:29:20 -0400, legg wrote: > >>On Fri, 07 Jun 2024 15:19:50 -0700, john larkin wrote: >> >>>On Fri, 07 Jun 2024 09:35:38 -0400, legg wrote: >>> >>>>On Thu, 6 Jun 2024 14:01:04 -0700, Don Y >>>>wrote: >>>> >>>>>On 6/6/2024 10:45 AM, legg wrote: >>>>>> On Mon, 3 Jun 2024 07:52:58 -0700, Don Y >>>>>> 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. >>>>> >>>>>Yes, but is it (measured)? Or, actively designed with as a target? >>>>> >>>>>Or, do you just use rules of thumb knowing that the typical *operating* >>>>>environment is likely to be X and chose components specified for Y > X >>>>>(but not necessarily Y >> X)? >>>>> >>>>>Note this iPhone claims a max operating of 93F and storage of 113F. >>>>>It is now 108F outside -- does that mean I can't use it outdoors? >>>>>And, when the temperature climbs to 115, I'll have to set it in an >>>>>ice bath? (I'm being facetious, of course). >>>>> >>>>>I suspect there isn't a place in the lower 48 that doesn't >>>>>see ambient temperatures above 93F at least part of the year. >>>>> >>>>>And, Apple isn't a garage shop with few design/test resources at >>>>>its disposal. >>>>> >>>>>So, clearly there is margin in these specifications. Whether it >>>>>is intended -- and to what extent -- is my point. >>>>> >>>>>When designing for industrial/commercial applications, we were always >>>>>extremely careful to *ensure* our products would operate in the temperature >>>>>ranges (and other environmental factors) that we specified. A fisherman >>>>>out on the North Atlantic would be miffed if his kit stopped working >>>>>because it was too cold or too hot (or, too much salt spray). A craftsman >>>>>would be annoyed if the tip of his screwdriver sheared off from "excessive" >>>>>torque. >>>>> >>>>>Similarly, a factory floor can't shut down because it's an unusually >>>>>warm day in the shop... >>>>> >>>>>Consumer kit *seems* to have a far more cavalier attitude towards >>>>>these things. And, one that doesn't really hold up to close inspection >>>>>(e.g., the iPhone). >>>>> >>>>> >>>>The guidelines are derived from empirical data and accelerating >>>>factors are determined. The arrhenius equation comes to mind. >>>> >>>>Predictors determine the design guidelines, but, yes, varying >>>>degrees of physical testing is a standard element in design and >>>>product verification. >>>> >>>>Commercial considerations of free enterprise have always pushed >>>>human behaviour towards banditry, so what can I tell you? >>>> >>>>RL >>> >>>That's entirely wrong. Whether you make spears or helicopters, you >>>need repeat business. >> >>Tell it to the bandits. There are plenty of suckers out there and >>paper/internet bumph easily generated to suit them. > >You can buy Sony or cheap no-name Chinese junk. Your choice. Would you >prefer to not have a choice? > >>> >>>Communist thugs are the genocidal bandits. They have a captive market >>>and no competition. >> >>Compared to the large-scale kleptocracies that replaced them? . . . > >The US and Europe have antitrust laws that pretty well ensure multiple >suppliers and competition. The real kleptocracy, in the USA or in >Russia or in China, is the government. In the US, the govt ensures that wall street is not inconvenienced. Assets are stripped to pay dividends, labor juggled for a similar benefit. Industry in north america is just not delivering. > >If you don 't want to buy a car from Honda, GM, Ford, Toyota, Kia, >Tesla, VW, or BMW, walk in the rain and snow like most of your >ancestors did. Few of our ancestors could afford a horse. You're forgetting BYD, Brilliance, Chery, Changfeng, Geely, Great Wall or any of the european-name-brand subsidiaries in India. I've only ever paid for one car - had to pay for the telephone pole it was totalled against, as well (it was that long ago). Anyways - a bit of a non-sequitur , neh? RL