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Fujitsu Could Help Smartphone Chips Run Cooler
angry tapir writes: If parts of your phone are sometimes too hot to handle, Fujitsu may have the answer: a thin heat pipe that can spread heat around mobile devices, reducing extremes of temperature. Fujitsu Laboratories created a heat pipe in the form of a loop that's less than 1mm thick. The device can transfer about 20W, about five times more heat than current thin heat pipes or thermal materials, the company said.
And desktops. That would reduce the fans work (and their own heat!) and the ugly noise that comes out of it.
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It certainly would be; however, that's not something Fujitsu specializes in, so they're sticking to what they're good at. This will also save power, in a less than obvious way; as chips get hotter, their internal resistance increases, causing them to draw more current, causing them to get hotter still, pushing the internal resistance up higher, causing them to draw yet more current. Keeping chips cooler actually causes them to draw less power, overall. Even with cooler-running chips that barely sip power, something like this is useful to keep them cool and efficient.
APK quotes people (including myself) without context and should not be trusted. Just thought you should know.
Normally current decreases as resistance increases. Why is chip power management different?
(no snark intended. I really want to know.)
Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
Because the parent got one word wrong. Typically resistance decreases as temperature increases in semiconductors, not the other way around. Metallic conductors behave in the opposite way.
Preface: I'm not qualified to discuss this in more detail than layman's terms will allow. I'm sure someone more qualified will step in and clear things up (and correct any inaccuracies in my information), and welcome them to do so.
You're thinking of resistance as a current-limiting mechanism, and you're absolutely correct in that respect. What happens, though, as the resistance of the signal path through a CPU increases, the switching current of the gates of the individual transistors in that data path also increases. This increase in switching current is greater than the current-limiting effect of the added resistance, increasing the over-all current draw of the chip.
That explanation is surely chock full of WTF-level inaccuracies, so don't quote me on that; standing by for correction.
APK quotes people (including myself) without context and should not be trusted. Just thought you should know.
Sign in and pick up some karma. I just posted an explanation that you can correct in more detail than what you posted here. Undo the damage I've done, please? :)
APK quotes people (including myself) without context and should not be trusted. Just thought you should know.
Rds increases as temperature increases in MOSFET's.
It's BJT's that decrease as temperature increases.
Plenty of phones sub-10mm today. 1mm is not an insignificant piece of the thickness budget.
This won't make your phone cooler; the manufacturers will just push their chips harder for the same temperature.
Just do that and go directly to Stockholm (Sweden) to immediately receive a Nobel prize.
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The efficiency at UHF depends on other factors. The temperature coefficient of Rds or Vce(sat) isn't the issue.
What matters here is THERMAL resistance, or if you prefer, call it by the inverse, thermal conductivity. It's just about moving the heat around to get it out. Semiconductors fail when junction temperatures are too high.
In a laptop, the use of similar devices makes sense, as the heat can be transferred
somewhere where it can be dissipated into the air. Unfortunately it's more efficient
to transfer it to the table you have it on, so the bottom gets the heatsink which
makes it horrible to actually put your laptop on your lap-top.
In a smartphone, it's being held in your hand (on the back) and up to your face (on
the front) with fingers on the sides. Where to exactly are they going to move the
heat??? Heat exchanging is nothing new, but the ability to remove heat requires
the device interact with a cooler medium to transfer that heat. Normally that's
your palm, or the air, or both.
So... I ask again... transfer the heat to where?
E
I seriously doubt this is going to have applications in people's smart phones. The limiting factor to pretty much all mobile performance issues is battery capacity, and being able to put more power through a certain mm^2 of silicon isn't going to help if you can't supply that power in the first place. This looks like a PR stunt by a component maker. These sorts of efficient heat pipes certainly have their place in many types of electronics products, most certainly in laptops and maybe even the next line of crossover tablet devices. But for smartphones I think we will need to wait for a significant improvement in battery tech before we have enough heat to waste that these things become any more useful than just sticking the chip to a big aluminium case like Apple does.
Some of that is actually pretty okay, but the bit you're missing is that CMOS used in most microprocessors effectively draws no gate current. Sure you need to charge up the gate but that quantity is not appreciably related to the switching resistance beyond the fact that you want to switch a gate as fast as possible to minimise time in the active region.
An entirely different principle.
In undoped semiconductor resistance will usually decrease as temperature is raised because a higher temperature excites more electrons into the conduction band where they can carry current.
But for cases where there is already a lot of charge the opposite usually applies. In something like a MOSFET the electrons are supplied by the source contact or in a doped bulk semiconductor there will be lots of charge from dopants. In these cases increasing the temperature doesn't significantly increase the charge. However raising the temperature does increase the electron scattering rate which reduces the electron mobility and slows electrons down, so the resistance actually increases.
Thank you for that, I actually wasn't sure of the mechanism by which what I said was made correct, if that makes any sense. It's been decades since it's been explained to me, so I only remembered the end result (increased resistance) and not why that, paradoxically, was the case.
APK quotes people (including myself) without context and should not be trusted. Just thought you should know.