SC2041

© 2000 SEMTECH CORP.

HotSwitch™ USB Power Distribution

Switch With Shutdown

July 18, 2000

652 MITCHELL ROAD NEWBURY PARK CA 91320

13

TYPICAL APPLICATIONS CIRCUITS (Cont.)

High-Power or Low-Power Bus-Powered Function:

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

must draw less than 100mA at startup. At this time,

they must also present a load of less than the parallel

combination of a 44

Ω resistor and a 10µF capacitor.

After startup, high powered functions may then draw up

to 500mA. The circuit below utilizes the SC2041 to

provide inrush current limiting and power switching for

the internal function.

Since USB is a hot insertion and removal system, USB

ports are subject to electrostatic discharge (ESD). The

SR05 provides ESD protection on the upstream data

and power lines. With proper layout the port is hard-

ened to greater than 15kV, meeting the requirements of

IEC 1000-4-2. The SC5205 LDO regulator is used to

power the hub controller from the upstream bus.

Note:

(1) 33µF output capacitor per port meets the USB specification minimum capacitance of 120µF per hub.

C1

10uF

C4

0.1uF

Upstream Port

D+

D-

VBUS

GND

C3

4.7uF

U2

SC5205-3.3

1

2

3

4

5

VIN

GND

EN

BYP

VO

C5

10uF

R1

100k

C2

10nF

U1

SR05

1

2

3

4

1

23

4

U3

SC2041

1

2

3

4

5

6

7

8

GND

IN

IN

SHDN

FLG

OUT

OUT

OUT

USB Controller

D0D+

D0D-

VCC

EN

OC

Internal Function

VCC

GND