SC5826

© 2000 SEMTECH CORP.

HotSwitch™

USB Power Distribution Switch

PRELIMINARY - February 18, 2000

652 MITCHELL ROAD NEWBURY PARK CA 91320

7

TYPICAL APPLICATIONS

Figure 2 - Bus-powered hub with ganged port power management

Bus-powered hub, ganged port power

management:

A bus-powered hub distributes power and data from an

input port to downstream ports. It must supply a con-

tinuous 100mA of current to each downstream port. A

bus-powered hub must be able to switch power to

downstream ports to prevent illegal device hook-up.

Inrush current limiting is also required to prevent power

supply drooping. The circuit below utilizes the SC5826

to provide ganged port power switching, inrush current

limiting and overcurrent protection for maximum port

protection. In a ganged switch configuration, all ports

are switched simultaneously. Under fault conditions,

the USB controller will remove power to all of the

ganged ports. For individual port management, an ad-

ditional SC5826 may be used.

Since USB is a hot insertion and removal system, USB

ports are subject to electrostatic discharge (ESD). The

SRDA05-4 provides ESD protection on the down-

stream data and power lines. Each device will protect

two USB ports. With proper layout the port is hard-

ened to greater than 15kV, meeting the requirements

of IEC 1000-4-2. On the upstream port, the LCDA05

provides ESD protection to the above levels for one

line pair. The SC5203 (or SC5205) LDO regulator is

used to power the hub controller from the upstream

bus.