TPS2074, TPS2075

FOUR-PORT USB HUB POWER CONTROLLERS

SLVS288A – SEPTEMBER 2000 – REVISED FEBRUARY 2001

21

POST OFFICE BOX 655303

APPLICATION INFORMATION

USB power-distribution requirements

USB can be implemented in several ways, and, regardless of the type of USB device being developed, several

power-distribution features must be implemented.

–

Current-limit downstream ports

–

–

Output 5.25 V to 4.75 at 500 mA

–

Enable/disable power to downstream ports

–

Power up at <100 mA

–

Limit inrush current (<44

Ω and 10 µF)

–

Output 5.25 V to 4.4 at 100 mA

–

Not send power back upstream

–

Limit inrush currents

–

Power up at <100 mA

–

Not send power back upstream (SP functions)

The feature set of the TPS2074 and TPS2075 allows them to meet each of these requirements. The integrated

current-limiting and overcurrent reporting is required by hosts and self-powered hubs. The logic-level enable

and controlled rise times meet the needs of both input and output ports on hubs, as well as the input ports for

bus-powered functions

USB hybrid hub

A USB hybrid hub can be simply implemented using the TPS2075 USB power controller and a TUSB2046 USB

hub controller as shown in Figure 33. The TPS2075 USB power controller provides all the power needs to the

four downstream ports and meets all the USB power specifications for both self-powered hubs and bus-powered

hubs. The power controllers integrated 3.3-V LDO is used to provide power for the hub controller and any other

local functions (e.g. transient suppressor SN75240 ), which saves board space and cost. The TPS2075 also

provides the hub controller with a power good (PG) signal that connects to the RESET input of the hub controller

to automatically reinitialize the hub when switching between self-powered mode and bus-powered mode

whenever the self-power supply is connected or disconnected. The amount of time in which the hub controller

is kept in a reset state is controlled by a capacitor connected between the PG_DLY pin of the power controller

and ground.