SC5826

© 2000 SEMTECH CORP.

HotSwitch™

USB Power Distribution Switch

PRELIMINARY - February 18, 2000

652 MITCHELL ROAD NEWBURY PARK CA 91320

6

TYPICAL APPLICATIONS

Figure 1 - Self-powered hub with individual port power management

Self-powered hub, indidual port power

management:

A self-powered hub must supply a continuous 500mA

of current to each downstream port. Since an internal

power supply is used to supply the power, self-powered

hubs are required to implement overcurrent protection

for safety. The self-powered hub must also have a

method to detect and report fault conditions to the USB

controller. The circuit below utilizes the SC5826 to pro-

vide individual port overcurrent protection & power

switching for maximum port protection. Under fault

conditions, the SC5826 provides the short-circuit cur-

rent limiting function and has a fault flag logic output for

notifying the hub controller. The USB hub can use the

SC5826 to remove power from the faulty port, allowing

the other ports to operate normally.

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.