5 V Slew-Rate Limited Half- and Full-Duplex

RS-485/RS-422 Transceivers

ADM4850–ADM4857

Rev. 0

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FEATURES

EIA RS-485-/RS-422-compliant

Data rate options

ADM4850/ADM4854—115 kbps

ADM4851/ADM4855—500 kbps

ADM4852/ADM4856—2.5 Mbps

ADM4853/ADM4857—10 Mbps

Half- and full-duplex options

Reduced slew rates for low EMI

True fail-safe receiver inputs

5 µA (maximum) supply current in shutdown mode

Up to 256 transceivers on one bus

Outputs high-z when disabled or powered off

−7 V to +12 V bus common-mode range

Thermal shutdown and short-circuit protection

Pin-compatible with MAX308x

Specified over the −40°C to +85°C temperature range

Available in 8-lead SOIC and LFCSP packages

APPLICATIONS

Low power RS-485 applications

EMI-sensitive systems

DTE-DCE interfaces

Industrial control

Packet switching

Local area networks

Level translators

FUNCTIONAL BLOCK DIAGRAM

RO

R

A

B

DI

D

Z

Y

GND

ADM4854/ADM4855/

ADM4856/ADM4857

RO

RE

R

DE

DI

D

A

B

GND

ADM4850/ADM4851/

ADM4852/ADM4853

Figure 1.

GENERAL DESCRIPTION

The ADM4850−ADM4857 are differential line transceivers

suitable for high speed half- and full-duplex data communication

on multipoint bus transmission lines. They are designed for

balanced data transmission and comply with EIA Standards

RS-485 and RS-422. The ADM4850−ADM4853 are half-duplex

transceivers, which share differential lines and have separate

enable inputs for the driver and receiver. The full-duplex

ADM4854−ADM4857 transceivers have dedicated differential

line driver outputs and receiver inputs.

The parts have a 1/8-unit-load receiver input impedance, which

allows up to 256 transceivers on one bus. Since only one driver

should be enabled at any time, the output of a disabled or pow-

ered-down driver is three-stated to avoid overloading the bus.

The receiver inputs have a true fail-safe feature, which ensures a

logic high output level when the inputs are open or shorted.

This guarantees that the receiver outputs are in a known state

before communication begins and when communication ends.

The driver outputs are slew-rate limited to reduce EMI and data

errors caused by reflections from improperly terminated buses.

Excessive power dissipation caused by bus contention or by

output shorting is prevented with a thermal shutdown circuit.

The parts are fully specified over the commercial and industrial

temperature ranges, and are available in 8-lead SOIC and LFCSP

packages.

Table 1. Selection Table

Part No

Half-/Full-Duplex

Data Rate

ADM4850

Half

115 kbps

ADM4851

Half

500 kbps

ADM4852

Half

2.5 Mbps

ADM4853

Half

10 Mbps

ADM4854

Full

115 kbp

ADM4855

Full

500 kbps

ADM4856

Full

2.5 Mbps

ADM4857

Full

10 Mbps