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Boost Converter PCB Layout

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peter.mitchell:
Couple of quick things;
Where are you going to connect Vin, GND and Vout?
Your feedback pin, put the corner of the L up the top, and then stitch your ground plane near the caps and switch.
If not a production board, I'd strongly consider not using thermal reliefs on the switches, it's easy to rework if they don't solder correctly, and it will lower impedance and improve dissipation. Maybe on inductor too.

Electr0nicus:

--- Quote from: peter.mitchell on January 15, 2014, 04:48:50 am ---Couple of quick things;
Where are you going to connect Vin, GND and Vout?
Your feedback pin, put the corner of the L up the top, and then stitch your ground plane near the caps and switch.
If not a production board, I'd strongly consider not using thermal reliefs on the switches, it's easy to rework if they don't solder correctly, and it will lower impedance and improve dissipation. Maybe on inductor too.


--- End quote ---

At Vin, GND and Vout there will be 1x4 pinheaders.  One for Vin (2 pins Vin, 2 pins GND) and one for Vout (2 pins Vout, 2 pins GND).
As these layouts are currently only conceptual, not all components are completly routed :)
Yes you are right with the inductor. If i rotate it 90° the SW- node copper area will be smaller. And yes stitching the GND planes will be done later on in the routing process. But as long as you moving components  around during layouting, having lots of stitching vias will make your work much harder, as you need to move them too.
And for the hand assembled PCBs  i will omit the termals. To change that, only a few clicks are necessary in EAGLE.

nickm:
I hate to rock the boat but I think your first layout is better.  The second one is a big U shape and the only way to keep the loop area small is to make the return path run all the way back around as a second big U. 

The biggest issue with your layouts is the grounds.  There will be high currents flowing all over your large ground plane which goes under your IC and is bad (Even worse in the second layout).  You should really control them and make 3 distinct grounds (power, analog, and the rest).  Break up your ground so that there is one power path which is big and beefy and runs directly under the outputs caps, FETs, L and input caps.  Then star your analog ground right at the ground pins of your input and output caps.  Putting a 0ohm in between your power and analog and power grounds makes it easy to isolate them in layout.  Then fill the rest of the board with ground and star that back to the input/output cap ground pins (optional).  This will garauntee that your high currents only flow where they should and everything else stays isolated and quiet.

Your analog ground could be better because its pretty broken up.  Rotate R9 180 degrees and place its pin right on the top of the IC.  Rotate that other cluster of stuff CCW 90 degrees and this will minimize the distance the grounds are from the ICs ground.

Again I think your first is pretty good, just get your grounds controlled, everything tighter and you should be good.

Hamed_ta:
Hi

Is there any update on your job ?

Hamed_ta:
can anyone check this too ?

https://www.eevblog.com/forum/projects/ltc3786-3v-to-18v-boost-converter/msg2783694/#msg2783694

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