TPS2061, TPS2062, TPS2063
TPS2065, TPS2066, TPS2067
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SLVS490B–DECEMBER 2003–REVISED DECEMBER 2004
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
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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