| Electronics > Projects, Designs, and Technical Stuff |
| How to heat-sink properly the PWD13F60 |
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| ali_asadzadeh:
Hi, I have an application that I think these new devices would help a lot, but the problem is what is the best way to design it so it could achieve maximum heat dissipation, in a fan-less design! can we get 8A out of it? have you done any project with them? |
| senso:
Good thermals pads and holes in the pcb to mount them against the case/pads? And 8A is the absolute maximum current DC, I wouldn't design anything going by absolute maximum ratings.. A fly farts in another room and it all explodes. |
| ali_asadzadeh:
--- Quote ---A fly farts in another room and it all explodes. --- End quote --- :-DD :-DD :-DD I would agree with that, But I thought the max was 32A ;) |
| Siwastaja:
Look at the datasheet: Absolute maximum ratings (these have little to no margin; you have to add your own): Id, DC when "case bottom pad" is at 25 degC = 8A. This means, if you have some imaginary perfect heatsink with some refrigeration compressor thingie running, so that you can actually force the pad to stay at 25 degC, while removing the heat, then you can run at 8A. For a more realistic application, look at this: Id, DC when "case bottom pad" is at 100 degC = 6.9A. Now, 100 degC pad temperature is realistic. If your ambient (near the PCB) is at 60 degC max, you'll have 40 degC gradient to play with, when your current is at 6.9A. You need to understand this DC number totally ignores switching losses. If your switching frequency is small compared to the edge rate, you may be able to ignore it, but OTOH, in many real-world cases, switching losses can be 50% of the total losses easily. In which case, you are down to 6.9A/sqrt(2) = 4.9A. So, expect around 4-6A out of this puppy. Which is still around 2 kW of actual power delivered at the intended DC bus voltage, through such a small device! Now, if you apply very thorough and well though out heatsinking techniques, and your switching losses are almost nonexisting, you might be able to push the current up to around 7A, but that has little margin left. This would be achievable with aluminium core PCB mounted to a heatsink with thermal pad material. If you can't do that, using 2oz copper and adding 0.4-0.5mm thermal vias filled with copper under the chip - then mounting the board with thermal pad to a heatsink - helps as well. If you can't have copper-filled vias, then you need to add standard vias just outside the chip area. Some homework for you: read about 1) switching losses, 2) thermal resistance calculations so that you understand what Table 4 means and how to apply it to your design. Finally, a sanity check: You are expecting this part to drive motors (or function as a part of EV fast charger, etc.) at 32A * 600V = 20kW. Assuming 99% efficiency (which may be unrealistic!), you would be dissipating 200W. Is it realistic for such a small package? Maybe this 10x13 millimeter $3 SMD part is not meant to drive 20kW motors/things, which normally are driven by massive modules inside $5000 products. |
| ali_asadzadeh:
Thanks Siwastaja, It helped a lot, 2Kw is certainly more than enough for my app! :) I wanted to know have someone attached an aluminum heat-sink to these kinds of babies!? because almost all the passives around them have a higher height! |
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