On Donnerstag, 9. April 2020 03:58:11 CEST Hal Murray wrote: > What's the problem with digital gear at cold temperatures? The only one I > can think of is that electrolytic capacitors stop working when the > electrolyte freezes.
The two most common problems are that gates switch too fast so timing margin disappears and leakage gets too low so that the biasing of semi-floating nodes (in dynamic circuits, say) can't be maintained. If the part isn't qualified for low temperatures to start with you can also have with breakdown and latch- up problems. Some degradation mechanisms are also accelerated at cold temperature, so lifetime goes down. The fun thing is that none of the functional problems might happen when the temperature goes down gradually while the part is continually operating (due to self-heating) but you might not be able to power up gear that has been sitting in the cold overnight. Testing at cold is already spectacularly difficult because every little remnant of moisture wants to freeze on the stuff you're trying to test, but when you need to also test for cold soaking then you really wish that this wasn't part of the specification. Plus you not only need to qualify all the parts, but after that the components and the whole system as well. If you have the power available, just specifying a more comfortable ambient temperature inside the cabinet is going to massively reduce the effort on that front (that's still tricky because you'll want non- condensing conditions at all time and maybe a few other things). > Do signal integrity problems appear when the rise time from CMOS drivers > gets faster? That can happen too. > What sort of warmth did the telecom guys decide they needed? I live in > California, at sea level rather than up in the mountains. We get occasional > freezing from radiation cooling on clear nights. They wouldn't have to > work very hard to keep a box above freezing. I'll have to look closer the > next time I see some cell phone antennas. Last time I've peeked into one it simply had a small shrouded fan heater in there. It's easy enough to figure out what amount of power is sufficient to achieve whatever delta-T at minimum ambient you're targeting and if that still fits your power budget you're done. Regards, Achim. -- +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+ Waldorf MIDI Implementation & additional documentation: http://Synth.Stromeko.net/Downloads.html#WaldorfDocs _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.