DS485

Low Power RS-485/RS-422 Multipoint Transceiver

General Description

The DS485 is a low-power transceiver for RS-485 and

RS-422 communication. The device contains one driver and

one receiver. The drivers slew rate allows for operation up to

2.5 Mbps (see Applications Information section).

The transceiver draws 200 µA of supply current when un-

loaded or fully loaded with the driver disabled and operates

from a single +5V supply.

The driver is short-circuit current limited and is protected

against excessive power dissipation by thermal shutdown

(High Impedance state) under fault conditions. The driver

guarantees a minimum of 1.5V differential output voltage

with maximum loading across the common mode range

(V

The receiver has a failsafe feature that guarantees a

logic-high output if the input is open circuit.

The DS485 is available in surface mount and DIP packages

and is characterized for Industrial and Commercial tempera-

ture range operation.

Features

n Meets TIA/EIA RS-485 multipoint standard

n Low quiescent current:

200 µA typ

n −7V to +12V common-mode input voltage range

n TRI-STATE outputs on driver and receiver

n AC performance:

— Driver transition time:

25 ns typ

— Driver propagation delay:

40 ns typ

— Driver skew:

1 ns typ

— Receiver propagation delay:

200 ns typ

— Receiver skew:

20 ns typ

n Half-duplex flow through pinout

n Operates from a single 5V supply

n Allows up to 32 transceivers on the bus

n Current-limiting and thermal shutdown for driver

overload protection

n Industrial temperature range operation

n Pin and functional compatible with MAX485 and LTC485

Connection and Logic Diagram

Order Number

Temp. Range

Package/###

DS485N

0˚C to +70˚C

DIP/N08E

DS485M

0˚C to +70˚C

SOP/M08A

DS485TN

−40˚C to +85˚C

DIP/N08E

DS485TM

−40˚C to +85˚C

SOP/M08A

Truth Table

DRIVER SECTION

DE

DI

A

B

X

HHH

L

XH

L

L

H

XLX

ZZ

RECEIVER SECTION

DE

A-B

RO

LL

≥+0.2V

H

LL

≤−0.2V

L

HX

X

Z

L

L

H

X = indeterminate

Z = TRI-STATE

DIP and SOIC

DS012880-1

July 1998

© 1999 National Semiconductor Corporation

DS012880

www.national.com