TPS2061, TPS2062, TPS2063

TPS2065, TPS2066, TPS2067

SLVS490I – DECEMBER 2003 – REVISED OCTOBER 2009

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UNDERVOLTAGE LOCKOUT (UVLO)

An undervoltage lockout ensures that the power switch is in the off state at power up. Whenever the input

voltage falls below approximately 2 V, the power switch is quickly turned off. This facilitates the design of

hot-insertion systems where it is not possible to turn off the power switch before input power is removed. The

UVLO also keeps the switch from being turned on until the power supply has reached at least 2 V, even if the

switch is enabled. On reinsertion, the power switch is 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 12-Mb/s, or 1.5-Mb/s, multiplexed serial bus designed for

low-to-medium bandwidth PC peripherals (e.g., keyboards, printers, scanners, and mice). The four-wire USB

interface is 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:

•

Hosts/self-powered hubs (SPH)

•

Bus-powered hubs (BPH)

•

Low-power, bus-powered functions

•

High-power, bus-powered functions

•

Self-powered functions

SPHs and BPHs distribute data and power to downstream functions. The TPS206x has higher current capability

than required by one USB port; so, it can be used on the host side and supplies power to multiple downstream

ports or functions.

HOST/SELF-POWERED AND BUS-POWERED HUBS

Hosts and SPHs have a local power supply that powers the embedded functions and the downstream ports (see

Figure 27). This power supply must provide from 5.25 V to 4.75 V to the board side of the downstream

connection under full-load and no-load conditions. Hosts and SPHs are required to have current-limit protection

and must report overcurrent conditions to the USB controller. Typical SPHs are desktop PCs, monitors, printers,

and stand-alone hubs.

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