On 09/28/2016 12:03 PM, Trumpeter wrote: > The one on my newly built kit gets pretty warm. Normal? I'm not an ee > so go easy on me :) >
It depends. (always a good answer. :-) My rule of thumb is to keep the maximum junction temperature somewhere between two thirds and three quarters of the data sheet's absolute max. If you know the operating condition then you can push closer to the max. But for our induction heaters, for example, which might be operated in 100 deg ambient and bright sun, I set the protective circuitry to around two thirds. You must calculate backwards from the chip, through the substrate/chip junction, through the substrate (package) to the heat sink and from the heat sink to air. If you use an insulator between the device and heat sink then you have two more junctions to account for. Calculating the heat flow can be tedious so I've attached a spreadsheet that automates all that tedium. John -- John DeArmond Tellico Plains, Occupied TN http://www.tnduction.com <-- THE source for induction heaters http://www.neon-john.com <-- email from here http://www.johndearmond.com <-- Best damned Blog on the net PGP key: wwwkeys.pgp.net: BCB68D77 -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/af25b97b-3d61-1290-ae03-40ff0c1f9176%40neon-john.com. For more options, visit https://groups.google.com/d/optout.
Thermal_resistance.ods
Description: application/vnd.oasis.opendocument.spreadsheet
