FUNCTIONAL DESCRIPTION

TUSB2551A

TERMINAL FUNCTIONS

TERMINAL

NO.

I/O

DESCRIPTION

NAME

RGT

PW

System interface supply voltage. Used to provide reference supply voltage for system I/O interface

15

1

I

signaling.

Speed. Edge-rate control: A logic HIGH operates at edge rates for full-speed operation. A logic LOW

SPEED

1

2

I

operates at edge rates for low-speed operation.

RCV

2

3

O

Receive data. Output for USB differential data.

If OE = 1, VP = Receiver output (+)

VP

3

4

I/O

If OE = 0, VP = Driver input (+)

If OE = 1, VM = Receiver output (–)

VM

4

5

I/O

If OE = 0, VM = Driver input (–)

SOFTCON

5

6

I

GND

6

7

Ground reference

SUSPEND

7

8

I

Suspend. Active high. Turns off internal circuits to reduce supply current.

NC

8, 16

No internal connection

Output enable. Active low. Enables the transceiver to transmit data onto the bus. When inactive, the

OE

9

9

I

transceiver is in the receive mode.

D–, D+

10, 11

10, 11

I/O

Differential data lines conforming to the USB standard

3.3-V reference supply. Requires a minimum 0.1-

µF decoupling capacitor for stability. A 1-µF capacitor is

12

12

O

recommended.

Pullup supply voltage. Used to connect 1.5-k

Ω pullup speed detect resistor.

13

13

O

14

14

I

USB bus supply voltage. Used to power USB transceiver and internal circuitry.

FUNCTION SELECTION

SUSPEND

OE

D+, D–

RCV

VP, VM

FUNCTION

0

0

Driving

Active

Active

Normal transmit mode

0

1

Receiving

Active

Active

Normal receive mode

1

0

Hi-Z

0

Not active

Low power state

1

1

Hi-Z

0

Active

(1)

During suspend, VP and VM are active to detect out-of-band signaling conditions.

TRUTH TABLE DURING NORMAL MODE

OE = 0

INPUT

OUTPUT

RESULT

VP

VM

D+

D–

RCV

0

0

0

0

SE0

0

1

0

1

0

Logic 0

1

0

1

0

1

Logic 1

1

1

1

1

Undefined

OE = 1

INPUT

OUTPUT

RESULT

D+

D–

VP

VM

RCV

0

0

0

0

SE0

0

1

0

1

0

Logic 0

1

0

1

0

1

Logic 1

1

1

1

1

Undefined

(1)

X = Undefined

Copyright © 2009, Texas Instruments Incorporated

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Product Folder Link(s): TUSB2551A