1

®

FN6050.2

ISL8487, ISL81483, ISL81487

1/8 Unit Load, 5V, Low Power, High Speed

or Slew Rate Limited, RS-485/RS-422

Transceivers

These Intersil RS-485/RS-422 devices are “fractional” unit

load (UL), BiCMOS, 5V powered, single transceivers that

meet both the RS-485 and RS-422 standards for balanced

communication. Unlike competitive devices, this Intersil

family is specified for 10% tolerance supplies (4.5V to 5.5V).

The ISL81483 and ISL81487 present a 1/8 unit load to the

RS-485 bus, which allows up to 256 transceivers on the

network for large node count systems (e.g., process

automation, remote meter reading systems). The 1/4 UL

ISL8487 allows up to 128 transceivers on the bus. In a

remote utility meter reading system, individual (apartments

for example) utility meter readings are routed to a

concentrator via an RS-485 network, so the high allowed

node count minimizes the number of repeaters required to

network all the meters. Data for all meters is then read out

from the concentrator via a single access port, or a wireless

link.

Slew rate limited drivers on the ISL8487 and ISL81483

reduce EMI, and minimize reflections from improperly

terminated transmission lines, or unterminated stubs in

multidrop and multipoint applications. Data rates up to

250kbps are achievable with these devices.

Data rates up to 5Mbps are achievable by using the

ISL81487, which features higher slew rates.

Receiver (Rx) inputs feature a “fail-safe if open” design,

which ensures a logic high Rx output if Rx inputs are

floating.

Driver (Tx) outputs are short circuit protected, even for

voltages exceeding the power supply voltage. Additionally,

on-chip thermal shutdown circuitry disables the Tx outputs to

prevent damage if power dissipation becomes excessive.

These half duplex devices multiplex the Rx inputs and Tx

outputs to allow transceivers with Rx and Tx disable

functions in 8 lead packages.

Features

• Fractional Unit Load Allows up to 256 Devices on the Bus

• Specified for 10% Tolerance Supplies

• Class 3 ESD Protection (HBM) on all Pins. . . . . . . . >7kV

• High Data Rate Version (ISL81487). . . . . . . up to 5Mbps

• Slew Rate Limited Versions for Error Free Data

Transmission (ISL8487, ISL81483) . . . . . . .up to 250kbps

• Low Current Shutdown Mode (Except ISL81487) . . . 1nA

• Low Quiescent Supply Current:

• -7V to +12V Common Mode Input Voltage Range

• Three State Rx and Tx Outputs

• 30ns Propagation Delays, 5ns Skew (ISL81487)

• Half Duplex Pinouts

• Operate from a Single +5V Supply (10% Tolerance)

• Current Limiting and Thermal Shutdown for driver

Overload Protection

• Drop-In Replacements for: MAX487 (ISL8487); MAX1483

(ISL81483); MAX1487, LMS1487 (ISL81487)

Applications

• High Node Count Networks

• Automated Utility Meter Reading Systems

• Factory Automation

• Security Networks

• Building Environmental Control Systems

• Industrial/Process Control Networks

TABLE 1. SUMMARY OF FEATURES

PART

NUMBER

HALF/FULL

DUPLEX

NO. OF DEVICES

ALLOWED ON BUS

DATA RATE

(Mbps)

SLEW-RATE

LIMITED?

RECEIVER/

DRIVER ENABLE?

QUIESCENT

LOW POWER

SHUTDOWN?

PIN

COUNT

ISL8487

Half

128

0.25

Yes

Yes

100

Yes

8

ISL81483

Half

256

0.25

Yes

Yes

100

Yes

8

ISL81487

Half

256

5

No

Yes

250

No

8

Data Sheet

December 2003

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.

1-888-INTERSIL or 321-724-7143

Copyright © Intersil Americas Inc. 2003. All Rights Reserved

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