Datasheet

TPS2041, TPS2051
POWER-DISTRIBUTION SWITCHES
SLVS172A –AUGUST 1998 – REVISED APRIL 1999
18
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
low-power bus-powered functions and high-power bus-powered functions
Both low-power and high-power bus-powered functions obtain all power from upstream ports; low-power
functions always draw less than 100 mA; high-power functions must draw less than 100 mA at powerup and
can draw up to 500 mA after enumeration. If the load of the function is more than the parallel combination of
44 Ω and 10 µF at powerup, the device must implement inrush current limiting (see Figure 32).
IN
OC
EN
GND
0.1 µF
2,3
5
4
6, 7, 8
0.1 µF 10 µF
GND
1
OUT
TPS2041
Power Supply
D+
D–
V
BUS
USB
Control
3.3 V
10 µF
Internal
Function
Figure 32. High-Power Bus-Powered Function
USB power-distribution requirements
USB can be implemented in several ways, and, regardless of the type of USB device being developed, several
powe- distribution features must be implemented.
Hosts/self-powered hubs must:
– Current-limit downstream ports
– Report overcurrent conditions on USB V
BUS
Bus-powered hubs must:
– Enable/disable power to downstream ports
– Power up at <100 mA
– Limit inrush current (<44 Ω and 10 µF)
Functions must:
– Limit inrush currents
– Power up at <100 mA
The feature set of the TPS2041 and TPS2051 allows them to meet each of these requirements. The integrated
current-limiting and overcurrent reporting is required by hosts and self-powered hubs. The logic-level enable
and controlled rise times meet the need of both input and output ports on bus-power hubs, as well as the input
ports for bus-power functions (see Figure 33).