EEVblog #744 - SMD Thermal Case Design - µSupply Part 15

[cypherpunks]

Remember, the outer layers start with 1/2 oz (17 µm) copper.  Then you drill PTHs, add a ghost-thin layer of electroless copper, and plate on an additional 17 µm to get the final desired trace thickness.

So the inside of vias are generally 1/2 oz thick.  You may lose a bit because the plating solution doesn't mix as rapidly in the confined area.

This is important when computing electricalor thermal resistance.

[T3sl4co1l]

BGAs can be heatsinked from on top, same as any; many high-performance FPGAs, etc. have a metal top.  Power devices are also designed to sink through the pads (which could be pretty good, seeing as solder balls are solid metal... but vias are not).

Usual heatsinking method is a spongy thermal pad, so the force is small.  A thinner pad (or straight grease) could be used, but then the surfaces need to mate closely.  An example might include the spring loaded brackets common in laptops (which also use BGAs or flip-chips for all the important parts: CPU, GPU, system chip, memory..).

Tim

[EEVblog]

Nice to see that you are working on the µSupply again. Will you update the project page in the near future, or is there a plan when the µSupply should be finished?

No plan. But yes it's being worked on.

[jb79]

Hello!

I'm trying to redesign Rev. C of the µSupply for myself to get more current out of it (3A), therefore I'll use the LT3083, maybe 2 of them in parallel.
It should be powered by 24V DC, so I'll place a DC/DC preregulator instead of the battery powered solution.

To get a more exact current measurement, I plan to use the INA219 in the circuit but I'll remove one of the 10Ohm resistors (R1) and replace it by a 1Ohm resistor in series with 2x10Ohm resistors in parallel. So the total shunt resistance for the opamps there will be still 1 Ohm but I get the possibility to get 1/10 of the voltage over the current shunt to measure by the INA219. Together with /8 measurement this will give me up to 3,2A total measurement range on the INA219. Of cause I take care about the power dissipation in the shunt resistors.

To get 3A out it is also necessary to change the voltage divider R25/R36. At it's output there should be 3,072mV to get 1mA/bit out of the 3,3V PWM signal.
To keep the different parts low I came out with the following values: R25=11k (10k+1k), R36=150k, resulting in only 0,08% error for the divider, the tolerance of the resistors is much higher. If only one 10k resistor for R25 is used, the error would be 0,71%.

Any other issues to deal with, when I try to get 3A out of the supply?

[BobC]

Nice to see that you are working on the µSupply again. Will you update the project page in the near future, or is there a plan when the µSupply should be finished?

No plan. But yes it's being worked on.

I just hit a situation where I need precisely this supply!  While I'd love to get the thing already built and boxed, I'd be more than happy settle for the Gerbers (or PCB) and a BOM (or kit).