Quote from: sensei on May 04, 2013, 07:31:31 PM

Both a barrel jack and a Molex pcie power connector may be a good option. For those who wish to power this as a separate unit instead of housing a bunch and running them off an ATX power supply.

I would consider a right angle Molex PCIe connector.

The PCIe is placed at the correct distance in from board edge so that either a right or straight connector will work.

Quote from: sensei on May 04, 2013, 07:27:37 PM

I would suggest a higher density of vias for the thermal pad. Here is an example of ones that we do for power drivers.

I could easily increase it and I may still. My brief research indicated 1.5mm spacing as optimal. It may be worth spending $10 for test boards with 15,25,36 via pads and a bundle of 1/2W resistors placed around the pad body to simulate, before ordering final boards. Or with the prototype board use one bank of 16 and one of 25 to test difference.

Quote from: ecliptic on May 04, 2013, 05:03:09 PM

If you can, i'd recommend adding fiducial markers on the silkscreen, both a few on the corners of the board, and local ones by each QFN [dot by pin 1]. for the board ones you can do a circle of copper on the top layer (with no soldermask) as well

Also i've been reading a few design notes on QFN heatsinking - it might be worth using 2 or even 3oz copper on the internal ground plane for added heat conduction, but i need to do some testing more more reading - just something to be aware of

How are you doing the layer stackup? Which layer is the power/ground plane?

Definitely plan to add and the silkscreen now is just what Kicad did by default. I haven't looked at it yet for adding what I want and removing garbage like "PIN1".

I was working with a rather basic 1.6mm stack:

top 1.2V plane, 1oz
0.2 FR4
inner 1 3.3V plane, 0.5oz
1.2 FR4
inner 2 signal, 0.5oz
0.2 FR4
bottom GND plane, 1oz

But there is more GND planes under the switching supply, and a few signals escape on inner 1.

I'm open to suggestions but something unusual will push the board cost up. Part of keeping the cost down is that they batch with other boards, so go weird and it will likely push cost by 5-10x or more (for short runs anyway). I'd consider using a thin board to help heat pass to the back more easily and I can go 1.2mm total for the same cost. I'm just unsure of the downside to that.

Quote from: sensei on May 04, 2013, 11:07:17 PM

I didn't see a thermistor in the BOM for the board temperature.

I'm using the temperature sensor built in to the PIC chip. It's not located under an ASIC die but then we can't have 16 sensors anyway, and this should be some average being close to one end of the board. I think it will be enough to calibrate a temp/fan speed relationship but obviously not an accurate die temp reading.