TPS2041B, TPS2042B
TPS2043B, TPS2044B, TPS2051B
TPS2052B, TPS2053B, TPS2054B
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SLVS514G–APRIL 2004–REVISED OCTOBER 2006
APPLICATION INFORMATION (continued)
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
TPS204xB/TPS205xB can provide-power distribution solutions to 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 Figure 30 and Figure 31). 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.
Power Supply
Downstream
USB Ports
3.3 V 5 V
TPS2041B
D+
D−
2, 3
0.1 µF
IN
6, 7, 8
V
BUS
OUT
0.1 µF
120 µF
GND
5
4
OC
EN
USB
Control
GND
1
Figure 30. Typical One-Port USB Host / Self-Powered Hub
20
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