**Note:** If you want to use this data for designing your own PCBs, please ensure that my stackup data matches what OSH Park is currently using.

Here’s some data on the OSH Park 4 layer stackup:

If you want a 50 ohm trace on the top layer and the second layer is ground (as it should be) then you want the trace width to be 14.47 thousands of an inch:

I used Agilent LineCalc this time. It performs an actual e-mag simulation to synthesize the correct line width. I am quite confident that this is the correct value given the inputs.

Nice write up.

I am just getting into differential pairs and was wondering why you have the Z0e set to 100 instead of the Z0.

Furthermore, what values might you recommend for USB 90 ohm differential pairs using the OSH Park 4-Layer Stackup.

Thank You.

I think you caught a mistake on my part. Thank you for notifying me.

As you’ve figured out, I’m not an expert on trace impedance.

Putting the numbers into Wcalc, I come up with the following for a 90 ohm differential coupled microstrip:

Using kicad’s calculator it seems that 0.15mm traces with 0.15mm spacing are 97.6 ohm Zdiff, which is close enough to 100 ohms that it’ll suffice for most stuff.

Are you sure? I’ve calculated your traces using kicad and TXLine. Both of them show about 70 Ohms impedance for your traces.

I’ve lost the images from my website as you can see. I will update this post and hopefully you will agree with my new calculations. Thank you for commenting.

It would be great if you calculated 100 Ohms line too 😉