1
\$\begingroup\$

I'm currently routing a board and need to supply 12A between a current sensing IC and an ESC. Due to size constraints I cannot have both the decoupling capacitor and IC on the same side of the board. Is it better to use a single large via to pass this trace between the top and bottom sides of the board, or would several smaller vias be better?

\$\endgroup\$
1
\$\begingroup\$

A single via that would happily carry 12A is a pretty big via for someone who says they don't have a lot of room. Have you checked out Saturn PCB toolkit?

Its via tool will give you an idea of the current handling vs temperature rise of a given via. You might want to consider filled vias too and think about your copper plating thickness etc.

\$\endgroup\$
  • \$\begingroup\$ The traces to and from the decoupling capacitor shouldn't need to carry 12A. \$\endgroup\$ – evildemonic Dec 14 '17 at 21:56
  • \$\begingroup\$ @evildemonic so what do you think a decoupling capacitor on an ESC (of all things) is doing if it's not participating in the I/O current??? \$\endgroup\$ – Neil_UK Dec 15 '17 at 6:09
  • \$\begingroup\$ @Neil_UK The decoupling capacitor is in parallel with the load, it does not carry the full load current. \$\endgroup\$ – evildemonic Dec 15 '17 at 15:22
  • \$\begingroup\$ @evildemonic what happens when the load demand changes so quickly that it cannot draw current through the impedance that connects it to the supply? If you did not want the voltage to fall where would the current come from then? \$\endgroup\$ – Some Hardware Guy Dec 15 '17 at 15:26
  • \$\begingroup\$ I'm not saying we don't want low impedance paths to the capacitor. I'm saying the traces to and from the decoupling capacitor don't need to handle the full load current. Worst case scenario source voltage instantaneously goes to zero, the load might try to draw up to 12A, but this is a decoupling capacitor, not a bulk cap that is going to try and power the load. Are we expecting 100% ripple? \$\endgroup\$ – evildemonic Dec 15 '17 at 18:50
0
\$\begingroup\$

As current capacity depends basically in copper width and plating thickness it will basically be the same to have, for example, two vias of 0,3mm diameter or one unique via of 0,6mm diameter, in both cases plating thickness being the same.

Here you can check an interesting article about this topic. At the end of the text there´s small explanation on this ("Multiple Vias").

\$\endgroup\$
  • \$\begingroup\$ Just to comment that current capacity depends in copper width, height and plating thickness. \$\endgroup\$ – user6127833 Dec 15 '17 at 10:25

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.