DS36277

Dominant Mode Multipoint Transceiver

General Description

The DS36277 Dominant Mode Multipoint Transceiver is de-

signed for use on bi-directional differential busses. It is opti-

mal for use on Interfaces that utilize Society of Automotive

Engineers (SAE) J1708 Electrical Standard.

The device is similar to standard TIA/EIA-485 transceivers,

but differs in enabling scheme. The Driver’s Input is normally

externally tied LOW, thus providing only two states: Active

(LOW), or Disabled (OFF). When the driver is active, the

dominant mode is LOW, conversely, when the driver is dis-

abled, the bus is pulled HIGH by external bias resistors.

The receiver provides a FAILSAFE feature that guarantees a

known output state when the Interface is in the following con-

ditions: Floating Line, Idle Line (no active drivers), and Line

Fault Conditions (open or short). The receiver output is

HIGH for the following conditions: Open Inputs, Terminated

Inputs (50

Ω), or Shorted Inputs. FAILSAFE is a highly desir-

able feature when the transceivers are used with Asynchro-

nous Controllers such as UARTs.

Features

n FAILSAFE receiver, RO = HIGH for:

— OPEN inputs

— Terminated inputs

— SHORTED inputs

n Optimal for use in SAE J1708 Interfaces

n Compatible with popular interface standards:

— TIA/EIA-485 and TIA/EIA-422-A

— CCITT recommendation V.11

n Bi-directional transceiver

— Designed for multipoint transmission

n Wide bus common mode range

— (−7V to +12V)

n Available in plastic DIP and SOIC packages

Connection and Logic Diagram

Truth Tables

Driver

Inputs

Outputs

DE

DI

DO/RI

DO /RI

LL

L

H

LH

H

L

HX

Z

Z

Receiver

Inputs

Output

RE

DO/RI–DO /RI

RO

L

≥ 0mV

H

L

≤ −500 mV

L

L

SHORTED

H

L

OPEN

H

HX

Z

DS011384-1

Order Number DS36277TM or DS36277TN

See NS Package Number M08A or N08E

July 1998

© 1999 National Semiconductor Corporation

DS011384

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