ADM483E

Rev. A | Page 11 of 16

GENERAL INFORMATION

The ADM483E is a robust RS-485 transceiver that operates

from a single 5 V supply.

It is ideally suited for operation in electrically harsh environ-

ments or where cables may be plugged and unplugged. It is also

immune to high RF field strengths without special shielding

precautions. The ADM483E is intended for balanced data

transmission and complies with both EIA Standards RS-485 and

RS-422. It contains a differential line driver and a differential

line receiver; it is suitable for half-duplex data transmission

because the driver and receiver share the same differential pins.

The input impedance on the ADM483E is 12 kΩ, allowing up to

32 transceivers on the differential bus.

The ADM483E operates from a single 5 V ± 10% power supply.

Excessive power dissipation caused by bus contention or by

output shorting is prevented by a thermal shutdown circuit.

This feature forces the driver output into a high impedance state

if, during fault conditions, a significant temperature increase is

detected in the internal driver circuitry.

The receiver has a fail-safe feature that results in a logic high

output state if the inputs are unconnected (floating).

A high level of robustness is achieved using internal protection

circuitry, eliminating the need for external protection components

such as transorbs or surge suppressors.

Low electromagnetic emissions are achieved using slew limited

drivers, minimizing interference both conducted and radiated.

The ADM483E can transmit at data rates up to 250 kbps.

A typical application for the ADM483E is illustrated in Figure 23.

This figure shows a half-duplex link where data may be

transferred at rates up to 250 kbps. A terminating resistor is

shown at both ends of the link. This termination is not critical

because the slew rate is controlled by the ADM483E and

reflections are minimized.

The communications network can be extended to include

multipoint connections as shown in Figure 26. Up to 32

transceivers can be connected to the bus.

E

3

8

4

M

D

A

E

3

8

4

M

D

A

RS-485/RS-422 LINK

RO

DI

DE

DI

DE

B

A

GND

B

A

GND

RO

0.1µF

0.1µF

+5V

+5V

RE

RE

Figure 23. Typical Half-Duplex Link Application

Table 6 and Table 7 show the truth tables for transmitting and

receiving.

Table 6. Transmitting Truth Table

Inputs

Outputs

RE

DE

DI

B

A

X1

1

1

0

1

X1

1

0

1

0

0

0

X1

High-Z

High-Z

1

0

X1

High-Z

High-Z

Table 7. Receiving Truth Table

Inputs

Outputs

RE

DE

A − B

RO

0

0

≥ +0.2 V

1

0

0

≤ −0.2 V

0

0

0

Inputs O/C

1

1

0

X1

High-Z

ESD TRANSIENT PROTECTION SCHEME

The ADM483E uses protective clamping structures on its inputs

and outputs that clamp the voltage to a safe level and dissipate

the energy present in ESD (electrostatic discharge).

The protection structure achieves ESD protection up to ±15 kV

according to the Human Body Model.