TUSB4041IPAPRG4 datasheet(36/48 Pages) TI2

36 / 48 page

TUSB4041I

SLLSEK3E – JULY 2015 – REVISED SEPTEMBER 2017

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10 Power Supply Recommendations

10.1 TUSB4041I Power Supply

The user should implement VDD as a single power plane, as well as VDD33.

•

The VDD pins of the TUSB4041I supply 1.1-V (nominal) power to the core of the TUSB4041I device. 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

because of the high current draw on the power rail. The user may need to adjust the output of the core

voltage regulator to account for this, or select a ferrite bead with low DC resistance (less than 0.05 Ω).

•

The VDD33 pins of the TUSB4041I device supply 3.3-V power rail to the I/O of the TUSB4041I device. 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. Place the smaller decoupling capacitors as close to the

TUSB4041I power pins as possible with an optimal grouping of two capacitors of differing values per pin.

10.2 Downstream Port Power

•

A source capable of supplying 5 V and up to 500 mA per port must supply the downstream port power,

VBUS. The TUSB4041I signals can control the downstream port power switches. Leaving the downstream

port power as always enabled is also possible.

•

The VBUS of each downstream port requires a large-bulk low-ESR capacitor of 22 µF or larger to limit in-rush

current.

•

TI recommends the ferrite beads on the VBUS pins of the downstream USB port connections for both ESD

and EMI reasons. A 0.1-µF capacitor on the USB connector side of the ferrite provides a low-impedance path

to ground for fast rise time ESD current that might have coupled onto the VBUS trace from the cable.

10.3 Ground

TI recommends to use only one board ground plane in the design which provides the best image plane for signal

traces running above the plane. Connect the thermal pad of the TUSB4041I and any of the voltage regulators to

this plane with vias. An earth or chassis ground is implemented only near the USB port connectors on a different

plane for EMI and ESD purposes.

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