VDD should be implemented as a single power plane, as should VDD33.
- The VDD terminals of the TUSB4020BI-Q1 supply 1.1-V (nominal) power to the core of the TUSB4020BI-Q1. 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 may need to be adjusted to account for this or a ferrite bead with low DC resistance (less than 0.05 Ω) can be selected.
- The VDD33 terminals of the TUSB4020BI-Q1 supply 3.3-V power rail to the I/O of the TUSB4020BI-Q1. This power rail can be isolated from all other power rails by a ferrite bead to reduce noise.
- All power rails require a 10-µF capacitor or 1-µF capacitors for stability and noise immunity. These bulk capacitors can be placed anywhere on the power rail. The smaller decoupling capacitors should be placed as close to the TUSB4020BI-Q1 power pins as possible with an optimal grouping of two of differing values per pin.