Path: ...!feeds.phibee-telecom.net!2.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: Sat, 08 Jun 2024 00:25:25 -0400 Organization: A noiseless patient Spider Lines: 52 Message-ID: <11n76jpt2qpaq49a6ka0qd8a82o8231o05@4ax.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Injection-Date: Sat, 08 Jun 2024 06:23:34 +0200 (CEST) Injection-Info: dont-email.me; posting-host="b998c89dfdd7b1a702ad952991d8f536"; logging-data="2604788"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+LrBrr/7dwf+sxlJCRyNRK" Cancel-Lock: sha1:yp1NGIzZuIUXJvUx46sHZulLCZA= X-Newsreader: Forte Agent 4.2/32.1118 Bytes: 3428 On Fri, 7 Jun 2024 15:16:49 -0700, Don Y wrote: >On 6/7/2024 2:59 PM, legg wrote: >> On Fri, 7 Jun 2024 12:45:24 -0700, Don Y >> 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I want too know how much MORE than the published/unpublished operating 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