Implement VDD and VDD33 as a
single power planes.
- The VDD pins of the TUSB8042A supply 1.1V (nominal) power to the core of the TUSB8042A.
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 be adjusted to account for
this, or a ferrite bead with low DC resistance (less than 0.05Ω) can be selected.
- The VDD33 pins of the TUSB8042A supply 3.3V power rail to the I/O of the TUSB8042A. 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 TUSB8042A power pins as possible with an optimal grouping of two of differing
values per pin.