Datasheet

TPS2041A, TPS2042A, TPS2043A, TPS2044A
TPS2051A, TPS2052A, TPS2053A, TPS2054A
CURRENT-LIMITED POWER-DISTRIBUTION SWITCHES
SLVS247 – SEPTEMBER 2000
21
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
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 will be 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 will also keep the switch from being turned on until the power supply has reached at least 2 V, even if
the switch is enabled. Upon reinsertion, the power switch will be 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
Self-powered and bus-powered hubs distribute data and power to downstream functions. The TPS204xA and
TPS205xA can provide power-distribution solutions for many of these classes of devices.
host/self-powered and bus-powered hubs
Hosts and self-powered hubs have a local power supply that powers the embedded functions and the
downstream ports (see Figures 26 and 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.
IN
OC
EN
GND
0.1 µF
2, 3
5
4
7
0.1 µF 120 µF
GND
OUT
TPS2041A
Power Supply
D+
D–
V
BUS
Downstream
USB Ports
USB
Control
3.3 V 5 V
Figure 26. Typical One-Port Solution