Quoting Rikard Bosnjakovic : > 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". > > 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? It means they don't guarantee it to work (for example, it might not start), and if it does work, it may not be within specifications (for example, the output voltage might be high or low or it could conceivably oscillate or do other bad things). As others have said, Tj will be pretty close to Tc, and especially initially after an overnight cold soak with power off, that will likely be just about the same as Ta. In this case, it's dead easy to buy automotive rated parts such as the LM317BT which is guaranteed to work from -40=B0C to +125=B0C, or even military rated parts (-55=B0C to +150=B0C). I would buy parts rated for the actual temperature range, but more importan= tly perhaps make sure that your capacitors have acceptable values at those temperatures (esp. electrolytics), and generally be careful of anything analog-ish such as clock oscillators and so on. Given typical hockey arena environments and times when they are used (eg. 5:30am on a snowy winter weekend), I'm sure you'd like it to be robust and not require fixing. That said, I'd lay odds that the stock 'commercial' temperature range = LM317 will work just fine-- you're not close to the lower limit for = the automotive/mil parts, and it's really just the same chip inside = for all the types with different test parameters. Best regards, Spehro Pefhany -- = "it's the network..." "The Journey is the reward" s...@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist