Printer

With 4-Port Hub

(Self-Powered)

Scanner

Digital

Scanner

PC

With Root Hub

Monitor

With 4-Port Hub (Self-Powered)

TUSB2046B

TUSB2046BI

www.ti.com

SLLS413I – FEBRUARY 2000 – REVISED SEPTEMBER 2013

APPLICATION INFORMATION

A major advantage of USB is the ability to connect 127 functions configured in up to 6 logical layers (tiers) to a

single personal computer (see Figure 5).

Figure 5. USB-Tiered Configuration Example

Another advantage of USB is that all peripherals are connected using a standardized four-wire cable that

provides both communication and power distribution. The power configurations are bus-powered and self-

powered modes. The maximum current that may be drawn from the USB 5-V line during power up is 100 mA.

For the bus-powered mode, a hub can draw a maximum of 500 mA from the 5-V line of the USB cable. A bus-

powered hub must always be connected downstream to a self-powered hub unless it is the only hub connected

to the PC and there are no high-powered functions connected downstream. In the self-powered mode, the hub is

connected to an external power supply and can supply up to 500 mA to each downstream port. High-powered

functions may draw a maximum of 500 mA from each downstream port and may only be connected downstream

to self-powered hubs. Per the USB specification, in the bus-powered mode, each downstream port can provide a

maximum of 100 mA of current, and in the self-powered mode, each downstream port can provide a maximum of

500 mA of current.

Both bus-powered and self-powered hubs require overcurrent protection for all downstream ports. The two types

of protection are individual-port management (individual-port basis) or ganged-port management (multiple-port

basis). Individual-port management requires power-management devices for each individual downstream port,

but adds robustness to the USB system because, in the event of an overcurrent condition, the USB host only

powers down the port that has the condition. The ganged configuration uses fewer power management devices

and thus has lower system costs, but in the event of an overcurrent condition on any of the downstream ports, all

the ganged ports are disabled by the USB host.

Using a combination of the BUSPWR and EEDATA/GANGED inputs, the TUSB2046B supports four modes of

power management: bus-powered hub with either individual-port power management or ganged-port power

management, and the self-powered hub with either individual-port power management or ganged-port power

management. Texas Instruments supplies the complete hub solution with the TUSB2036 (2/3-port), TUSB2046B,

and the TUSB2077 (7-port) hubs along with the power-management devices needed to implement a fully USB

specification-compliant system.

Copyright © 2000–2013, Texas Instruments Incorporated

Submit Documentation Feedback

9

Product Folder Links: TUSB2046B TUSB2046BI