1

®

FN6051.7

ISL8487E, ISL81487L, ISL81487E

Low Power, High Speed or Slew Rate

Limited, RS-485/RS-422 Transceivers

These Intersil RS-485/RS-422 devices are ESD protected,

fractional unit load (UL), BiCMOS, 5V powered, single

transceivers that meet both the RS-485 and RS-422

standards for balanced communication. Each driver output/

receiver input is protected against ±15kV ESD strikes,

without latch-up. Unlike competitive devices, this Intersil

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

All devices 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). 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 ISL8487E and ISL81487L

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

ISL81487E, 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

• RS-485 I/O Pin ESD Protection . . . . . . . . . . ±15kV HBM

- Class 3 ESD Level on all Other Pins . . . . . . >7kV HBM

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

• Specified for 10% Tolerance Supplies

• High Data Rate Version (ISL81487E) . . . . . up to 5Mbps

• Slew Rate Limited Versions for Error Free Data

Transmission (ISL8487E, ISL81487L) . . . . .up to 250kbps

• Low Quiescent Supply Current:

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

• Three State Rx and Tx Outputs

• 30ns Propagation Delays, 5ns Skew (ISL81487E)

• Half Duplex Pinouts

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

• Current Limiting and Thermal Shutdown for Driver

Overload Protection

• Pin Compatible Replacements for: MAX487E, (ISL8487E);

LTC1487, ADM1487 (ISL81487L); MAX1487E, ST485ER

(ISL81487E)

• Pb-Free Plus Anneal Available (RoHS Compliant)

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

ISL8487E

Half

256

0.25

Yes

Yes

120

Yes

8

ISL81487L

Half

256

0.25

Yes

Yes

120

Yes

8

ISL81487E

Half

256

5

No

Yes

350

No

8

Data Sheet

February 27, 2006

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

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