TUSB2077A

7-PORT HUB FOR THE UNIVERSAL SERIAL BUS

WITH OPTIONAL SERIAL EEPROM INTERFACE

SLLS414 – MARCH 2000

12

POST OFFICE BOX 655303

APPLICATION INFORMATION

bus-powered hub, ganged port power management

When used in bus-powered mode, the TUSB2077A supports up to four downstream ports by controlling a

TPS2041 device which is capable of supplying 100 mA of current to each downstream port. Bus-powered hubs

must implement power switching to ensure current demand is held below 100 mA when the hub is hot-plugged

into the system. Utliizing the TPS2041 for ganged power management provides over-current protection for the

downstream ports. The SN75240 transient suppressors reduce inrush current and voltage spikes on the data

lines. The OVRCUR signals should be tied together for a ganged operation.

† TPS2041 and SN75240 are Texas Instruments devices.

‡ 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.

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

DP1

DM1

DP2

DM2

DP3

DM3

DP4

PWRON1

PWRON2

PWRON3

PWRON4

OVRCUR1

OVRCUR2

OVRCUR3

OVRCUR4

DM4

DP0

DM0

VCC

XTAL1

XTAL2

EXTMEM

RESET

SN75240†

EN

IN

OC

OUT

D +

D –

5 V

GND

D +

D –

5 V

D +

D –

5 V

D +

D –

5 V

Downstream

Ports

TUSB2077A

TPS2041†

A

B

C

D

100

SN75240†

A

B

C

D

GND

GND

GND

1

µF

100

100

100

5 V

3.3 V

GND

D +

D –

Upstream

Port

SN75240†

A

B

5 V

GND

C

D

4.7

µF

0.1

µF

4.7

µF

GND

Ferrite Beads

Ferrite Beads

Ferrite Beads

Ferrite Beads

EEDATA/GANGED

6-MHz Clock

Signal

BUSPWR

System

Power-On Reset

OUT

OUT

IN

3.3 V

1.5 k

Ω

15 k

Ω

15 k

Ω

15 k

Ω

15 k

Ω

15 k

Ω

15 k

Ω

15 k

Ω

15 k

Ω

DP5–DP7

DM5–DM7

PWRON5–7

OVRCUR5–7

NC

3.3 V

MODE

DP0PUR

Figure 9. TUSB2077A Bus-Powered Hub, Ganged Port Power Management Application