DS36C279

Low Power EIA-RS-485 Transceiver with Sleep Mode

General Description

The DS36C279 is a low power differential bus/line trans-

ceiver designed to meet the requirements of RS-485 Stan-

dard for multipoint data transmission. In addition it is compat-

ible with TIA/EIA-422-B.

The sleep mode feature automatically puts the device in a

power saving mode when both the driver and receiver are

applications where the device may be disabled for extended

periods of time.

ity. The driver outputs operate over the entire common mode

range of −7V to +12V. Bus contention or fault situations that

cause excessive power dissipation within the device are

handled by a thermal shutdown circuit, which forces the

driver outputs into a high impedance state.

The receiver incorporates a fail safe circuit which guarantees

The DS36C279T is fully specified over the industrial tem-

perature range (−40˚C to +85˚C).

Features

n 100% RS-485 compliant

— Guaranteed RS-485 device interoperation

n Low power CMOS design:

I

n Automatic sensing sleep mode

— Reduces I

n Built-in power up/down glitch-free circuitry

— Permits live transceiver intersection/displacement

n DIP and SOIC packages available

n Industrial temperature range:

−40˚C to +85˚C

n On-board thermal shutdown circuitry

— Prevents damage to the device in the event of

excessive power dissipation

n Wide common mode range:

−7V to +12V

n Receive open input fail-safe (Note 1)

≥ 128 nodes

≥ 64 nodes

n ESD (Human Body Model):

≥ 2kV

n Drop-in replacement for:

— LTC485 MAX485 DS75176 DS3695

Connection and Logic Diagram

Truth Table

DRIVER SECTION

RE*

DE

DI

DO/RI

DO*/RI*

XH

H

H

L

XH

L

L

H

XL

X

Z

Z

RECEIVER SECTION

RE*

DE

RI-RI*

RO

LL

≥+0.2V

H

LL

≤−0.2V

L

H

L

X

Z (Note 2)

L

L

OPEN (Note 1)

H

Note 1: Non-terminated, open input only

Note 2: Device enters sleep mode if enable conditions are held 600 ns

DS012053-1

Order Number DS36C279M, DS36C279N,

DS36C279TM or DS36C279TN

See NS Package Number M08A or N08E

July 1998

© 1999 National Semiconductor Corporation

DS012053

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