This section describes the layout recommendations for all of the TUSB4020BI-Q1 differential pairs: USB_DP_XX, USB_DM_XX.

• Must be designed with a differential impedance of 90 Ω ±10%.
• To minimize crosstalk, TI recommends to keep high-speed signals away from each other. Separate each pair by at least 5× the signal trace width. Separating with ground as depicted in the layout example also helps minimize crosstalk.
• Route all differential pairs on the same layer adjacent to a solid ground plane.
• Do not route differential pairs over any plane split.
• Adding test points causes impedance discontinuity, and therefore, negatively impacts signal performance. If test points are used, place the test points in series and symmetrically. The test points must not be placed in a manner that causes stub on the differential pair.
• Avoid 90° turns in trace. Keep the use of bends in differential traces to a minimum. When bends are used, make sure the number of left and right bends are as equal as possible and that the angle of the bend is ≥135°. Take this action to minimize any length mismatch caused by the bends, and therefore, minimize the impact bends have on EMI.
• Minimize the trace lengths of the differential pair traces. Eight inches is the maximum recommended trace length for USB 2.0 differential-pair signals. Longer trace lengths require very careful routing to assure proper signal integrity.
• Match the etch lengths of the differential pair traces (that is DP and DM). Make sure the USB 2.0 differential pairs do not exceed 50mil relative trace length difference.
• Minimize the use of vias in the differential-pair paths as much as possible. If this is not practical, ensure that the same via type and placement are used for both signals in a pair. Place any vias used as close as possible to the TUSB4020BI-Q1 device.
• Do not place power fuses across the differential-pair traces.