TPS2041B, TPS2042B
TPS2043B, TPS2044B, TPS2051B
TPS2052B, TPS2053B, TPS2054B
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SLVS514G–APRIL 2004–REVISED OCTOBER 2006
APPLICATION INFORMATION (continued)
Downstream
USB Ports
D+
D−
Power Supply
3.3 V
5 V
V
BUS
+
TPS2044B
33 µF
GND
2
IN1
IN2
15
OUT1
6
D+
D−
0.1 µF
14
11
V
BUS
OUT2
OUT3
+
33 µF
GND
16
OC1
EN1
OC2
EN2
OC3
EN3
OC4
EN4
3
D+
D−
13
4
USB
Controller
V
BUS
+
12
7
33 µF
10
GND
OUT4
9
D+
D−
8
V
GND GND
BUS
+
33 µF
GND
1
5
Figure 31. Typical Four-Port USB Host / Self-Powered Hub
Bus-powered hubs obtain all power from upstream ports and often contain an embedded function. The hubs are
required to power up with less than one unit load. The BPH usually has one embedded function, and power is
always available to the controller of the hub. If the embedded function and hub require more than 100 mA on
power up, the power to the embedded function may need to be kept off until enumeration is completed. This can
be accomplished by removing power or by shutting off the clock to the embedded function. Power switching the
embedded function is not necessary if the aggregate power draw for the function and controller is less than one
unit load. The total current drawn by the bus-powered device is the sum of the current to the controller, the
embedded function, and the downstream ports, and it is limited to 500 mA from an upstream port.
LOW-POWER BUS-POWERED 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 power up 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 power up, the device must implement inrush current limiting (see Figure 32).
21
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