0
\$\begingroup\$

I've designed a PCB for power distribution. I have a 90W (5V 18A) power supply that will be responsible for powering 5 USB Type-A outputs, each USB drawing up to 12.5W (5V 2.5A) MAX.

I'm used to PCB layout for low-power digital electronics but this will be the first time designing something drawing this much current.

I'm just trying to work out whether my PCB layout is sufficient to handle up to 12.5A current draw from the supply.

The Facts

Via's: 1.6mm Diameter, 0.9mm Hole
Fuses: Hold Current 1.6A, Trip Current 2.8A
Terminal: Rated Up to 1.6A
LEDs: Used for Status (wont turn on if fuse tripped)

enter image description here enter image description here

MY QUESTIONS:

  • Should I order 2oz copper?
  • Should I use via stitching and if so what kind of dimensions?
  • I made my via's large in hole size so I can put solder in them, is this necessary/advised?
\$\endgroup\$
1
\$\begingroup\$

I see you have thermal relief enabled on your pads, which means all the current will go through the four tiny 0.3mm bits of track around the pad in your input connector. It could be a good idea to use "direct connect style" on your polygon to avoid this.

Make sure the screw connectors can handle the current, it's in the specs.

If there are two connectors on the board, is this to daisy chain them? For high current it would be preferable to just route wires to the power supply from each board. You can also put the power connector in the middle instead of in a corner, current will have less copper to go through.

Don't worry about the copper, it'll work fine, resistance of 1oz copper plane is about 0.5 mOhm per square.

You can put several vias on the ground pin of the connectors: Place -> Fill, draw a copper rectangle, set its NET property, then place a few vias in it, for example on the side of the USB connector pin, you've got space for 3-4 vias.

Also you should rotate the fuse 90° and put it where the "R5" silkscreen is. Or you could put it at the side of the USB connector (with a wide trace). This is so the soldering iron can reach the pins of the USB connector without trouble.

These USB connectors have two thru hole pins to hold them to the board but they're pretty far away from the edge, which means quite important leverage, so they'll be fragile. You could use ones with the thru hole pins closer to the edge, or for DIY put 2 groun thru hole pads on either side of the connector and solder a bit of wire to strap the connector down on the board so it doesn't lift when it gets brutalized a bit.

\$\endgroup\$
3
  • \$\begingroup\$ Thankyou very much for this detailed reply, I'll use everything you've mentioned! No it isn't to daisy chain, I just and making multiple boards as the power supply has the potential to be on both the Left Hand Side or Right Hand side, so just designing the board so it has that flexibility. The fuse rotation is a great idea, ashamed I didn't consider that myself. I'm also not too concerned about the USB THT legs as I don't envision the cable will be inserted and removed frequently, if ever, however I guess theres not reason to make my design more rugged. \$\endgroup\$
    – Explorex
    Jun 1 at 12:30
  • \$\begingroup\$ Is there any reason why you wouldn't use "Direct Connect Style" wouldn't you always want your polygon pours to connect as much as possible to your pads? \$\endgroup\$
    – Explorex
    Jun 1 at 12:34
  • 1
    \$\begingroup\$ Direct connect sinks a lot of heat into the copper plane so if your soldering iron is a bit wimpy it'll be difficult to solder (and desolder). \$\endgroup\$
    – bobflux
    Jun 1 at 12:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.