1

LTC1487

Ultra-Low Power RS485

with Low EMI, Shutdown

and High Input Impedance

S

FEATURE

DESCRIPTIO

The LTC

ceiver designed with high impedance inputs allowing up to

256 transceivers to share a single bus. It meets the

requirements of RS485 and RS422. The LTC1487 features

output drivers with controlled slew rate, decreasing the

EMI radiated from the RS485 lines, and improving signal

fidelity with misterminated lines. The CMOS design offers

significant power savings without sacrificing ruggedness

against overload or ESD damage. Typical quiescent cur-

rent is only 80

µA while operating and 1µA in shutdown.

The driver and receiver feature three-state outputs, with

the driver outputs maintaining high impedance over the

entire common-mode range. Excessive power dissipation

caused by bus contention or faults is prevented by a

thermal shutdown circuit which forces the driver outputs

into a high impedance state. The receiver has a fail-safe

feature which guarantees a high output state when the

inputs are left open. I/O pins are protected against multiple

ESD strikes of over

±10kV using the Human Body Model.

The LTC1487 is fully specified over the commercial tem-

perature range and is available in 8-pin DIP and SO

packages.

s

High Input Impedance: Up to 256 Transceivers

on the Bus

s

s

s

1

µA Quiescent Current in Shutdown Mode

s

Controlled Slew Rate Driver for Reduced EMI

s

Single 5V Supply

s

ESD Protection to

±10kV On Receiver Inputs and

Driver outputs

s

– 7V to 12V Common-Mode Range Permits

±7V

Ground Difference Between Devices on the Data Line

s

Thermal Shutdown Protection

s

Power Up/Down Glitch-Free Driver Outputs Permit

Live Insertion or Removal of Transceiver

s

Driver Maintains High Impedance in Three-State

or with the Power Off

s

Pin Compatible with the LTC485

APPLICATI

TYPICAL

s

Battery-Powered RS485/RS422 Applications

s

Low Power RS485/RS422 Transceiver

s

Level Translator

S

APPLICATI

R

1

RO

120

Ω

RE

DE

DI

2

3

7

6

7

6

4

1

2

3

4

D

R

D

RO

RE

DE

DI

LTC1487 • TA01

120

Ω

330

Ω

LTC1487

LTC1487

EQUIVALENT LOAD OF 256

LTC1487 TRANSCEIVERS

2000 FEET OF TWISTED-PAIR WIRE

4.7nF

DI

A

B

RO

LTC1487 • TA02

, LTC and LT are registered trademarks of Linear Technology Corporation.