I'm having troubles calculating the characteristic impedance of USB/Ethernet traces for a pcb. The Saturn PCB design program calculates values where I'm not sure if they are correct. I want to use a 4 layer pcb of this kind:
The outside copper layers will be 70µm thick instead of the 18µm from the picture (the manufacturer confirmed that they can produce it). Also, εr=3,8 on outside layers.
The calculation with Saturn PCB Design gives the following values for USB:
The conductor width and conductor spacing values seem to be a bit odd. Especially the spacing is really huge, right? (TI: "Route DP/DM traces close together for noise rejection on differential signals".)
The program also shows a S/H warning in the picture.
Are these values indeed correct? Or are parameters wrong? I'm not sure about the base copper weight and plating thickness. As I want to have 70µm on outside layers, I summed the copper values (18+52=70).
What is this warning telling me? Or did I make a mistake?