It only takes a tiny bit of mutual impedance to bring the differential impedance down to 90, which is why your package puts them so far apart. Thus a 'differential pair' any long distance apart will have an impedance of 98 ohms, without any coupling between the lines, i.e. The calculation looks correct, but the tracks are too wide.įor example, a single 0.75 mm track on a 0.36 mm substrate, has an impedance to ground, unbalanced, of about 49 ohms.
