DS1487

General Description

The DS1487 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

2.0 Mbps (see Applications Information section). The trans-

to 128 nodes to be connected together without the use of re-

peaters.

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 DS1487 is available in surface mount and DIP pack-

ages.

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 Current-limiting and thermal shutdown for driver

overload protection

n Pin and functional compatible with MAX1487

Connection and Logic Diagram

Order Number

Temp. Range

Package/###

DS1487N

0˚C to +70˚C

DIP/N08E

DS1487M

0˚C to +70˚C

SOP/M08A

Truth Table

DRIVER SECTION

RE

(Note 1)

DE

DI

A

B

X

HHH

L

XH

L

L

H

XLX

ZZ

RECEIVER SECTION

RE

(Note 1)

DE

A-B

RO

LL

≥+0.2V

H

LL

≤−0.2V

L

HX

X

Z

L

L

OPEN (Note 1)

H

X = indeterminate

Z = TRI-STATE

Note 1: Non Terminated, Open Input only

DIP and SOIC

DS012920-1

*Note: Non Terminated, Open Input only

July 1998

© 1999 National Semiconductor Corporation

DS012920

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