TPS2014, TPS2015

POWER DISTRIBUTION SWITCHES

SLVS159B – DECEMBER 1996 – REVISED AUGUST 1997

18

POST OFFICE BOX 655303

APPLICATION INFORMATION

bus-powered and self-power hubs

Hubs provide data and power for downstream functions through output ports. Self-power hubs have internal

power supplies that furnish power to downstream functions. Each port is required to supply 500 mA continuous

to a downstream function. Each port must have overcurrent protection to meet the requlatory safety limit that

no single port can deliver more than 5 A. The self-power hub must also have a method to detect and report an

overcurrent condition to the USB host. The TPS20xx provides the required current-limiting function and has an

overcurrent logic output to inform the hub controller of the fault condition. The on-state resistance of the

TPS20xx is low enough to meet all USB voltage regulation requirements. The switch also provides the capability

to remove power from a faulted port.

Bus-powered hubs distribute power and data from an input port to downstream ports. Each output port is

required to supply 100 mA continuous. A bus-powered hub is not required to provide overcurrent protection

because it is provided by the upstream port. In order to power up in a low power state, the self-powered hub

must be able to switch power to its output ports. The TPS20xx can also provide this function.

Figure 25. Typical USB Self-Powered Hub Application

OUT

OUT

OUT

2

3

5

4

EN

OC

IN

IN

7

8

6

120

µF

0.1

µF

10 k

Ω

TPS2014

1

D-

D+

USB Port

Connector

GND

5 V

3.3 V

5 V

OVERCURRENT

LOAD ENABLE

D1+

D1-

USB

Controller

Power Supply

GND

SN75240

TUSB2040

0.1

µF

+

low power bus-powered functions and high power bus-powered functions

Low-power and high-power bus-powered functions are powered by their input ports. If the load of the function

is more than the parallel combination of 44

Ω and 10 µF, it must implement inrush current limiting. The TPS20xx

provides this function with its controlled rise time during turn on.