TPS2145, TPS2147

TPS2155, TPS2157

SLVS333 − AUGUST 2001

19

www.ti.com

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.

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Current-limit downstream ports

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−

Enable/disable power to downstream ports

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Power up at <100 mA

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Limit inrush current (<44

Ω and 10 µF)

−

Limit inrush currents

−

Power up at <100 mA

The feature set of the TPS2145 and TPS2147 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 need of both input and output ports on bus-powered hubs, as well as the input

ports for bus-powered functions.

USB applications

Figure 19 shows the TPS2147 being used in a USB bus-powered/self-powered peripheral design. The internal

3.3-V LDO is used to provide power for the USB function controller as well as to the 1.5-k

Ω pullup resistor.

In bus-powered mode, switch 1 provides power to the 5-V circuitry. In self-powered mode, switch 2 provides

power to the 5-V circuitry while the USB 5-V still provides power to the 3.3-V LDO (USB allows self-powered