The simplest of compact thermal models (CTMs) is a one resistor type. Of these the most widely quoted is Theta_ja (ok, ok, and Theta_jma, more on that variant later). Knowing the power dissipation of the component as well as the ambient temperature is in theory all that is required to determine the junction temperature from the supplied Theta_ja resistance value. You would … [Read more...]
Web slashes and missing polar ice
I read in the news this last week that Sir Tim Berners-Lee, a Brit and the inventor of the World Wide Web, has confessed that the // in a web address were actually “unnecessary”… and it seems that polar ice will be gone in the summer, perhaps by as early as 2020, opening the arctic ocean to shipping. At the same time I’m writing this on my laptop, the fan’s just … [Read more...]
So, you want to predict component temperatures do you? Part II
Lumped block package representation makes the best use of limited available data to simulate for an ‘indication’ of case temperature. Some indication is better than none but I wouldn’t bet on it, really, I wouldn’t. Accurate case and junction temperature prediction can only be realised with either a fully 3D detailed representation or an abstracted CTM … [Read more...]
What’s black and stuck on a PCB?
Hmmm… If you’re guessing it’s a chip package, you’re right – got it in one. Well done! OK, so what type of package is it? If you’re thinking it’s a silly question as you don’t know anything about the package, other than I’ve told you its black - that was a hint that it’s an encapsulated plastic part by the way - you’d be right. You’d need me to tell you if it had leads, and if … [Read more...]
The Better Box Model
Introduction For the consumer, natural convection cooling or fan-less cooling is the method of choice. It is silent, it is reliable, it is simple, and it is environmentally sound because no additional energy is used to remove the excess heat. For the thermal engineer, fan-less cooling is more problematic. On the plus side, no fan is needed, so there is an attractive cost … [Read more...]
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