DS481

Low Power RS-485/RS-422 Multipoint Transceiver with

Sleep Mode

General Description

The DS481 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 transceiver draws 200 µA of supply current when un-

loaded or 0.2 µA when in the automatic sleep mode. Sleep

mode is activated by inactivity on the enables (DE and RE

(Note 1)). Holding DE =L and RE (Note 1)=H for greater than

600 ns will enable the sleep mode. The DS481 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 DS481 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 128 transceivers on the bus (DS481N/M)

n Allows up to 64 tranceivers on the bus (DS481TN/M)

n Current-limiting and thermal shutdown for driver

overload protection

n Industrial temperature range operation

n Pin and functional compatible with MAX481C and

MAX481E

Connection and Logic Diagram

Order Number

Temp. Range

Package/###

DS481N

0˚C to +70˚C

DIP/N08E

DS481M

0˚C to +70˚C

SOP/M08A

DS481TN

−40˚C to +85˚C

DIP/N08E

DS481TM

−40˚C to +85˚C

SOP/M08A

Truth Table

DRIVER SECTION

RE

(Note 1)

DE

DI

A

B

XH

H

H

L

XH

L

L

H

X

L

X

Z

Z (Note 2)

RECEIVER SECTION

RE

(Note 1)

DE

A-B

RO

LL

≥+0.2V

H

LL

≤−0.2V

L

H

X

X

Z (Note 2)

L

L

OPEN (Note 1)

H

X = indeterminate

Z = TRI-STATE

Note 1: Non Terminated, Open Input only

DE = L and RE (Note 1) = H.

DS012919-1

*Note: Non Terminated, Open Input only

July 1998

© 1999 National Semiconductor Corporation

DS012919

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