I designed a Buck Converter for my senior design and need to put that on PCB which will power up the circuit.

enter image description here

I calculated the with of the trace for the current I need which is 8 Amps. Based on the calculation I need 0.13 inch of trace. My question is do I need to make the thickness of the traces same for the Capacitors as well or only thick traces for input and output of the buck converter. Since, capacitor only holds the voltage, I don't see the point of making the traces bigger for the capacitor. I need to make sure that my assumptions are right before I make the PCB order. The schematics of the converter and the traces are down below.

second pic is the traces pic

  • 4
    \$\begingroup\$ The capacitor doesn't just hold the voltage. It provides current during certain parts of the switching cycle. Consider using power planes instead of wide traces as appropriate. \$\endgroup\$
    – nanofarad
    Commented Oct 30, 2016 at 0:49
  • 3
    \$\begingroup\$ Your schematic is too small to read. Please post a larger version. In the meantime: What switching topology are you trying to create here? Why do some of the components on your board appear to not be connected to anything? \$\endgroup\$
    – user39382
    Commented Oct 30, 2016 at 1:26
  • 1
    \$\begingroup\$ ESR and ESL of the traces and Caps are considered for high pulsed currents \$\endgroup\$ Commented Oct 30, 2016 at 1:48
  • 2
    \$\begingroup\$ You should read some app notes on switching PSUs, see some layouts for eval kits, etc.. \$\endgroup\$
    – Wesley Lee
    Commented Oct 30, 2016 at 2:23
  • 1
    \$\begingroup\$ Consider fastest rise time as 1/3F then model all impedances in the loop including Zcap(f)+ESR , MOSFET RdsOn & Coss/Ciss, ZL(f) and lookup trace L , R from dimensions and consider crosstalk or add ground tracks/pour to reduce coupling. Ensure Vref ground has no ground shift from Load Current. \$\endgroup\$ Commented Oct 30, 2016 at 21:46

1 Answer 1


8 Amp is a whole lot of current and you need to understand where all this current will flow on the PCB. After this is understood you can go ahead and design the trace width for all the different connections. Also care needs to be taken so that the pads on the PCB is sufficiently large to transfer all this current. This is very important, you do not want the PCB to get too hot. I do not see any fuse on your schematic but that could also be good to add.

do I need to make the thickness of the traces same for the Capacitors

The current peak for the charge/discharge curve by a capacitor will be determined by the capacitors resistance and the voltage supplied. A capacitor of "normal" capacity will not be able to charge or discharge all that current (and this is perhaps not needed nor wanted), thus you will probably not need to make the traces as wide to these as you would otherwise.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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