High Speed, Isolated RS-485 Transceiver

with Integrated Transformer Driver

ADM2485

Rev. A

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FEATURES

Half-duplex, isolated RS-485 transceiver

Integrated oscillator driver for external transformer

PROFIBUS® compliant

Complies with ANSI/TIA/EIA RS-485-A-98 and

ISO 8482:1987(E)

Data rate: 16 Mbps

50 nodes on bus

High common-mode transient immunity: >25 kV/μs

Isolated DE OUT status output

Thermal shutdown protection

Safety and regulatory approvals

UL recognition: 2500 V rms for 1 minute per UL 1577

VDE Certificate of Conformity

DIN V VDE V 0884-10 (VDE V 0884-10):2006-12

Operating temperature range: –40°C to +85°C

Wide-body, 16-lead SOIC package

APPLICATIONS

Isolated RS-485/RS-422 interfaces

PROFIBUS networks

Industrial field networks

Multipoint data transmission systems

FUNCTIONAL BLOCK DIAGRAM

RTS

DE OUT

A

B

D1

D2

TxD

RxD

RE

ADM2485

OSC

Figure 1.

GENERAL DESCRIPTION

The ADM2485 differential bus transceiver is an integrated,

galvanically isolated component designed for bidirectional data

communication on multipoint bus transmission lines. It is

designed for balanced transmission lines and complies with

ANSI/TIA/EIA RS-485-A-98 and ISO 8482:1987(E).

The device employs Analog Devices, Inc., iCoupler® technology

to combine a 3-channel isolator, a three-state differential line

driver, and a differential input receiver into a single package. An

on-chip oscillator outputs a pair of square waveforms that drive

an external transformer to provide isolated power with an external

transformer. The logic side of the device can be powered with

either a 5 V or a 3.3 V supply, and the bus side is powered with

an isolated 5 V supply.

The ADM2485 driver has an active high enable. The driver

differential outputs and the receiver differential inputs are

connected internally to form a differential input/output port

that imposes minimal loading on the bus when the driver is

high receiver disable that causes the receive output to enter a

high impedance state.

The device has current-limiting and thermal shutdown features

to protect against output short circuits and situations where bus

contention might cause excessive power dissipation. The part is

fully specified over the industrial temperature range and is available

in a 16-lead, wide-body SOIC package.