DS36276

FAILSAFE Multipoint Transceiver

General Description

The DS36276 FAILSAFE Multipoint Transceiver is designed

for use on bi-directional differential busses. It is compatible

with existing TIA/EIA-485 transceivers, however, it offers an

additional feature not supported by standard transceivers.

The FAILSAFE feature guarantees the receiver output to a

known state when the Interface is in the following conditions:

Floating Line, Idle Line (no active drivers), and Line Fault

conditions (open or short). The receiver output is in a HIGH

state for the following conditions: OPEN Inputs, Terminated

Inputs (50

Ω), and SHORTED Inputs.

FAILSAFE is a highly desirable feature when the transceiv-

ers are used with Asynchronous Controllers such as UARTs.

Features

n FAILSAFE receiver, RO = HIGH for:

— OPEN inputs

— Terminated inputs

— SHORTED inputs

n Compatible with popular interface standards:

— TIA/EIA-485 (RS-485)

— TIA/EIA-422-A (RS-422-A)

— CCITT Recommendation V.11

n Bi-Directional Transceiver

— Designed for multipoint transmission

n Separate driver input, driver enable, receiver enable,

and receiver output for maximum flexibility

n Wide bus common mode range

— (−7V to +12V)

n Pin compatible with: DS75176B, DS96176, DS3695 and

SN75176A and B

n Available in SOIC package

Connection and

Logic Diagram

Truth Tables

Driver

Inputs

Outputs

RE

DE

DI

DO/RI

DO /RI

XH

H

H

L

XH

L

L

H

XLX

Z

Z

Receiver

Inputs

Output

RE

DE

RI–RI

RO

LL

≥0V

H

LL

≤−500 mV

L

HX

X

Z

Receiver FAILSAFE

Inputs

Output

RE

DE

RI–RI

RO

L

L

SHORTED

H

L

L

OPEN

H

HX

X

Z

DS011383-1

Order Number DS36276M

See NS Package Number M08A

July 1998

© 1999 National Semiconductor Corporation

DS011383

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