5 V, 0.8 mA PROFIBUS

RS-485 Transceiver

ADM1486

Rev. A

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FEATURES

Meets and exceeds EIA RS-485 and EIA RS-422 standards

30 Mbps data rate

Recommended for PROFIBUS applications

2.1 V minimum differential output with 54 Ω termination

Thermal shutdown and short-circuit protection

0.5 ns skew driver and receiver

Driver propagation delay: 11 ns

Receiver propagation delay: 12 ns

High impedance outputs with drivers disabled or power off

Superior upgrade for SN65ALS1176

Available in standard 8-lead SOIC package

APPLICATIONS

Industrial field equipment

GENERAL DESCRIPTION

The ADM1486 is a differential line transceiver suitable for high

speed bidirectional data communication on multipoint bus

transmission lines. It is designed for balanced data transmission,

complies with EIA Standards RS-485 and RS-422, and is recom-

mended for PROFIBUS applications. The part contains a

differential line driver and a differential line receiver. Both the

driver and the receiver may be enabled independently. When

disabled or powered down, the driver outputs are high impedance.

The ADM1486 operates from a single 5 V power supply.

Excessive power dissipation caused by bus contention or output

shorting is prevented by short-circuit protection and thermal

circuitry. Short-circuit protection circuits limit the maximum

output current to ±200 mA during fault conditions. A thermal

shutdown circuit senses if the die temperature rises above

150°C and forces the driver outputs into a high impedance state

under this condition.

Up to 50 transceivers may be connected simultaneously on a

bus, but only one driver should be enabled at a time. Therefore,

it is important that the remaining disabled drivers do not load

the bus.

FUNCTIONAL BLOCK DIAGRAM

ADM1486

R

D

RO

RE

DE

DI

B

A

GND

8

5

6

7

1

4

3

2

Figure 1.

To ensure this, the ADM1486 driver features high output

impedance when disabled and when powered down. This

minimizes the loading effect when the transceiver is not being

used. The high impedance driver output is maintained over the

entire common-mode voltage range from −7 V to +12 V.

The receiver contains a fail-safe feature that results in a logic

high output state if the inputs are unconnected (floating).

The ADM1486 is fabricated on BiCMOS, an advanced mixed

technology process combining low power CMOS with fast

switching bipolar technology. All inputs and outputs contain

protection against ESD; all driver outputs feature high source

and sink current capability. An epitaxial layer is used to guard

against latch-up.

The ADM1486 features extremely fast and closely matched

switching, enable, and disable times. Minimal driver propaga-

tion delays permit transmission at data rates up to 30 Mbps

while low skew minimizes EMI interference.

The part is fully specified over the commercial and industrial

temperature range and is available in an 8-lead SOIC package.