2

Truth Table

TRANSMITTING

INPUTS

OUTPUTS

RE

DE

DI

B / Z

A / Y

X

1101

X

1010

X

0

X

High-Z

High-Z

Truth Table

RECEIVING

INPUTS

OUTPUT

RE

DE

A-B

RO

00

≥ +0.2V

1

00

≤ -0.2V

0

0

0

Inputs Open

1

1

X

X

High-Z

Pin Descriptions

PIN

FUNCTION

RO

Receiver output: If A > B by at least 0.2V, RO is high; If A < B by 0.2V or more, RO is low; RO = High if A and B are unconnected (floating).

RE

Receiver output enable. RO is enabled when RE is low; RO is high impedance when RE is high.

DE

Driver output enable. The driver outputs, Y and Z, are enabled by bringing DE high. They are high impedance when DE is low.

DI

Driver input. A low on DI forces output Y low and output Z high. Similarly, a high on DI forces output Y high and output Z low.

GND

Ground connection.

A/Y

RS-485/422 level, noninverting receiver input and noninverting driver output. Pin is an input (A) if DE = 0; pin is an output (Y) if DE = 1.

B/Z

RS-485/422 level, inverting receiver input and inverting driver output. Pin is an input (B) if DE = 0; pin is an output (Z) if DE = 1.

System power supply input (4.5V to 5.5V).

Typical Operating Circuit

ISL81485

0.1

µF

+

D

R

7

6

8

1

2

3

4

5

GND

RO

RE

DE

DI

A / Y

B / Z

+5v

0.1

µF

+

D

R

6

7

8

1

2

3

4

5

GND

RO

RE

DE

DI

A / Y

B / Z

+5v

ISL81485