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IN1

OC1

EN1

OC2

EN2

GND

0.1

µF

2

16

3

13

4

15

14

33

µF

33

µF

GND

1

OUT1

OUT2

TPS2044B

Power Supply

D+

D−

GND

D+

D−

Downstream

USB Ports

USB

Controller

3.3 V

5 V

OC3

EN3

OC4

EN4

12

7

9

8

6

IN2

+

+

5

GND

11

10

33

µF

33

µF

GND

OUT3

OUT4

D+

D−

GND

D+

D−

+

+

LOW-POWER BUS-POWERED AND HIGH-POWER BUS-POWERED FUNCTIONS

TPS2041B,, TPS2042B

TPS2043B, TPS2044B, TPS2051B

TPS2052B, TPS2053B, TPS2054B

SLVS514E – APRIL 2004 – REVISED JANUARY 2006

APPLICATION INFORMATION (continued)

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.

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).

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