TUSB2077A

7-PORT HUB FOR THE UNIVERSAL SERIAL BUS

WITH OPTIONAL SERIAL EEPROM INTERFACE

SLLS414 – MARCH 2000

13

POST OFFICE BOX 655303

APPLICATION INFORMATION

self-powered hub, individual port power management

In a self-powered configuration, the TUSB2077A can be implemented for individual port-power management

when used with two TPS2044 because it is capable of supplying 500 mA of current to each downstream port

and can provide current limiting on a per port basis. When the hub detects a fault on a downstream port, power

is removed from only the port with the fault and the remaining ports continue to operate normally. Self-powered

hubs are required to implement over-current protection and report overcurrent conditions. The SN75240

transient suppressors reduce inrush current and voltage spikes on the data lines.

Figure 10. TUSB2077A Self-Powered Hub, Individual Port-Power Management Application

6-MHz Clock

Signal

BUSPWR

DP1

DM1

DP2

DM2

DP6

DM6

DP7

PWRON1

PWRON2

PWRON6

PWRON7

OVRCUR1

OVRCUR2

DM7

DP0

DM0

VCC

GND

XTAL1

XTAL2

EXTMEM

RESET

5 V

3.3 V

GND

D +

D –

Upstream

Port

SN75240†

EN1

OC1

D +

D –

5 V

GND

D +

D –

5 V

D +

D –

5 V

D +

D –

5 V

Downstream

Ports

5-V Board Power

Supply

TUSB2077A

TPS2044†

A

B

C

D

100

SN75240†

A

B

C

D

GND

GND

GND

100

100

100

† TPS2042 and SN75240 are Texas Instruments devices. Two TPS2042 devices can be substituted for

the TPS2044.

‡ 120

µF per hub is the minimum required per the USB specification, version 1.1. However, TI recommends a 100 µF low ESR tantulum capacitor

per port for immunity to voltage droop.

SN75240†

A

B

5 V

GND

C

D

4.7

µF

0.1

µF

4.7

µF

EN2

EN3

EN4

OC2

OC3

OC4

OUT4

OUT3

OUT2

OUT1

EEDATA/GANGED

System

Power-On Reset

IN1

0.1

µF

IN2

§ LDO is a 5 V to 3.3 V voltage regulator. TPS76333 from Texas Instruments can be used.

15 k

Ω

15 k

Ω

15 k

Ω

15 k

Ω

1.5 k

Ω

3.3 V

15 k

Ω

15 k

Ω

15 k

Ω

15 k

Ω

3.3 V

OVRCUR6

OVRCUR7

MODE

DP0PUR