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Class D Switching Power Amplifiers and Power D/A conversion

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Old 16th April 2010, 09:31 PM   #11
bwaslo is offline bwaslo  United States
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Maybe if the thermal interface was to a floating heatsink, pulled against the substrate by some low spring force?

edit: I guess that would mean a separate heatsink for each chip. Probably not a good idea

Last edited by bwaslo; 16th April 2010 at 09:33 PM. Reason: some rethinking
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Old 16th April 2010, 09:32 PM   #12
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You may have good luck using a thermal adhesive to bond and thin sheet fin to the die for test purposes, but anything other than a compressive load would probably bust it apart.
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Old 16th April 2010, 09:33 PM   #13
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Yeah, bwaslo, like the conventional CPU plan. Worst case you'd have to do a little sink for each die.
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Old 16th April 2010, 09:37 PM   #14
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I wonder how much of a thermal interface you'd get from the chip right to the board itself? The ICEpower boards use SOT mosfets with NO heatsink and seem to get away with it.

edit: the ASC200 boards, that is. Other modules are less adventurous about that.
edit the edit: make that the 200ASC boards.

Last edited by bwaslo; 16th April 2010 at 09:47 PM. Reason: clarification.. and correction
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Old 16th April 2010, 09:39 PM   #15
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I could also imagine that thermal coupling through a soft thermal gap filler pad might be sufficient.
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Old 16th April 2010, 11:16 PM   #16
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It all depends on where you want die temperature. You could make a Kapton printed circuit and clamp it into a sink with rubber/glass pads on both sides, or even graphite if you masked everything. Getting the signal and power around it all in a decent way. Yikes.
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Old 17th April 2010, 11:45 AM   #17
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Well, I believe these high-electron-mobility devices are just variations of microwave transistors and adapted to switched mode power. Still if you dig their docs, the demanded gate inductance is to be <2nH and Vgs never exceeding 6V for ~2.5V threshold. This calls for some serious RF-layout techniques and from this point of view I find the case quite friendly, you can try soldering that by reflow, infrared or even hotair.
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Old 27th April 2010, 06:33 PM   #18
bwaslo is offline bwaslo  United States
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Has anyone messed with these yet? Wondering how bad the package is to deal with.
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Old 27th April 2010, 06:42 PM   #19
bwaslo is offline bwaslo  United States
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just looked on their site, they now have a demo board available that looks like it might be tweaked into being a class D amp with some extra circuitry and without too much trouble. I haven't built a class D before other than mounting modules, so can any experienced builders comment on whether that might work? Thinking something like a UcD topologyhttp://epc-co.com/epc/documents/guides/EPC9002_qsg.pdf
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Old 27th April 2010, 07:10 PM   #20
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I'm not sure if I missed something.
The figure 2 (Id vs Vgs) of the document shows great linearity.
If that graph is truly plotted using test data instead of just being an illustration skatch, I think this MOSFet might be great for linear operation too, I.e. Class A/AB amps
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