On Dec 21, 2007 8:32 AM, Rikard Bosnjakovic wrote: > I'm having a couple of LM317:s which I'm about to use in a hockey > arena (with ambient temperature around -10 degrees Celcius). In the > datasheet - maximum ratings section - for the 317, I find "T_op > Operating junction temperature: 0-125". In this case, they are meaning that the device is guaranteed to meet the data sheet specs over that temperature range. On the high end, the chip will shut down, but on the low end, you're sort of "on your own" It may work ok, it may get itself into an odd state that it can't recover from, who knows. What I'd do, is test it. Set up the circuit, put it in the coldest environment that it could reasonably be asked to work in, let it sit for hours, so that it's all "cold soaked", the apply power and see what happens. Normally, we try to use devices within the data sheet parameters, but sometimes, we have to color outside the lines a bit. :) At the moment, I'm trying to find a device to replace a microprocessor's crystal, that won't be too much bothered by millisecond impacts of 2000Gs. So far, i'm having no luck finding anything that specs that high, and we may end up getting some pretty rugged devices, and testing them ourselves. Someone else suggested pre-heating the device, and that's not a bad option. Once it's operating and within the 0-125C range, it should be fine. > I'm a bit confused by "junction" in this statement. Does this mean > that an ambient temperature of -10 will make the LM317 unable to work, > or does it mean that it will be fine as long as the junction is no > colder than 0 degrees? When they say "junction", they mean that the actual physical chip, inside the plastic, is where the temperature matters, as opposed to outside on the plastic or on the heatsink. -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist