Implement VDD and VDD33 as a single power plane.
- The VDD terminals of the TUSB4020BI supply 1.1V (nominal) power to the core of the TUSB4020BI. This power rail can be isolated from all other power rails by a ferrite bead to reduce noise.
- The DC resistance of the ferrite bead on the core power rail can affect the voltage provided to the device due to the high current draw on the power rail. The output of the core voltage regulator can need to be adjusted to account for this or a ferrite bead with low DC resistance (less than 0.05Ω) can be selected.
- The VDD33 terminals of the TUSB4020BI supply 3.3V power rail to the I/O of the TUSB4020BI. This power rail can be isolated from all other power rails by a ferrite bead to reduce noise.
- All power rails require a 10µF capacitor or 1µF capacitors for stability and noise immunity. These bulk capacitors can be placed anywhere on the power rail. Place the smaller decoupling capacitors as close to the TUSB4020BI power pins as possible with an optimal grouping of two of differing values per pin.