SC2041

© 2000 SEMTECH CORP.

HotSwitch™ USB Power Distribution

Switch With Shutdown

July 18, 2000

652 MITCHELL ROAD NEWBURY PARK CA 91320

12

TYPICAL APPLICATIONS CIRCUITS (Cont.)

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 contin-

uous 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 SC2041

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,

additional SC2041s 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 downstream

data and power lines. Each device will protect two USB

ports. With proper layout the port is hardened to greater

than 15kV, meeting the requirements of IEC 1000-4-2.

On the upstream port, the SR05 provides ESD protec-

tion to the above levels for one line pair. The SC5205

LDO regulator is used to power the hub controller from

the upstream bus.

Ferrite Bead

Ferrite Bead

Ferrite Bead

Ferrite Bead

Ferrite Bead

Ferrite Bead

Ferrite Bead

USB Controller

D0D+

D0D-

VCC

EN

OC

D1D+

D1D-

OC

OC

OC

D2D+

D2D-

D3D+

D3D-

D4D+

D4D-

Downstream Port

VBUS

D+

D-

GND

Downstream Port

VBUS

D+

D-

GND

Downstream Port

VBUS

D+

D-

GND

C6

33uF

C7

33uF

C8

33uF

U1

SR05

1

2

3

4

1

23

4

U2

SC5205-3.3

1

2

3

4

5

VIN

GND

EN BYP

VO

U3

SC2041

1

2

3

4

5

6

7

8

GND

IN

IN

SHDN

FLG

OUT

OUT

OUT

Upstream Port

D+

D-

VBUS

GND

C2

10nF

C3

4.7uF

Downstream Port

VBUS

D+

D-

GND

C1

4.7uF

C4

0.1uF

R1 100k

U4

SRDA05-4

I/O1

I/O2

I/O3

I/O4

REF2

REF2

REF1

REF1

U5

SRDA05-4

I/O1

I/O2

I/O3

I/O4

REF2

REF2

REF1

REF1

Ferrite Bead

C5

33uF

Note:

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

hub.