TPS2140, TPS2141

TPS2150, TPS2151

SLVS399A − JANUARY 2002 − REVISED MAY 2006

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APPLICATION INFORMATION

undervoltage lockout (UVLO)

An undervoltage lockout ensures that the device (LDO and switch) is in the off state at power up. The UVLO

also keeps the device from being turned on until the power supply has reached the start threshold (see

undervoltage lockout table), even if the switches are enabled. The UVLO is also activated whenever the input

voltage falls below the stop threshold as defined in the undervoltage lockout table. This function facilitates the

design of hot-insertion systems where it is not possible to turn off the power switches before input power is

removed. Upon reinsertion, the power switches are turned on with a controlled rise time to reduce EMI and

voltage overshoots.

universal serial bus (USB) applications

The universal serial bus (USB) interface is a multiplexed serial bus operating at either 12 Mbps, or 1.5 Mbps

for USB 1.1, or 480 Mbps for USB 2.0. The USB interface is designed to accommodate the bandwidth required

by PC peripherals such as keyboards, printers, scanners, and mice. The four-wire USB interface was conceived

for dynamic attach-detach (hot plug-unplug) of peripherals. Two lines are provided for differential data, and two

lines are provided for 5-V power distribution.

USB data is a 3.3-V level signal, but power is distributed at 5 V to allow for voltage drops in cases where power

is distributed through more than one hub across long cables. Each function must provide its own regulated 3.3 V

from the 5-V input or its own internal power supply.

The USB specification defines the following five classes of devices, each differentiated by power-consumption

requirements:

The TPS2140/41/50/51 are well suited for USB hub and peripheral applications. The internal LDO can be used

to provide the 3.3-V power needed by the controller while the switch distributes power to the downstream

functions.

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

−

−

Enable/disable power to downstream ports

−

Power up at <100 mA

−

Limit inrush current (<44

Ω and 10 µF)

−

Limit inrush currents

−

Power up at <100 mA