Route RXP/N and TXP/N pairs with controlled 90-Ω differential impedance (±15%).
Keep away from other high speed signals.
In USB3
applications maintaining polarity through the TUSB1002A is not
necessary. Therefore, TI recommends connecting polarity in such a way that
produces the best routing.
Keep intra-pair routing to within 2 mils.
Intra-pair length matching must be near the location of mismatch.
Inter-pair length matching is not necessary.
Separate each pair at least by 3 times the signal trace width.
Keep the use of bends in differential traces to a minimum. When bends are used, the number of left and right bends should be as equal as possible and the angle of the bend should be ≥ 135 degrees. This minimizes any length mismatch causes by the bends; ad therefore, minimize the impact bends have on EMI.
Route all differential pairs on the same of layer.
The number of VIAS must be kept to a minimum. TI recommends keeping the VIAS count to 2 or less.
Keep traces on layers adjacent to ground plane.
Do NOT route differential pairs over any plane split.
When using thru-hole USB connectors, it is recommend to route differential pairs on bottom layer in order to minimize the stub created by the thru-hole connector.
Adding Test points causes impedance discontinuity; and therefore, negatively impact signal performance. If test points are used, they should be placed in series and symmetrically. They must not be placed in a manner that causes a stub on the differential pair.