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_______________General Description

The MAX3480A/MAX3480B are electrically isolated

RS-485/RS-422 data-communications interfaces.

Transceivers, optocouplers, and a transformer are all

included in one low-cost, 28-pin DIP package. A single

+3.3V supply on the logic side powers both sides of the

interface.

The MAX3480B features reduced-slew-rate drivers that

minimize EMI and reduce reflections caused by

improperly terminated cables, allowing error-free data

transmission at data rates up to 250kbps. The

MAX3480A’s driver slew rate is not limited, allowing

transmission rates up to 2.5Mbps.

These devices typically draw 180mA of quiescent sup-

ply current. The MAX3480B provides a low-power shut-

down mode in which it consumes only 0.2µA.

Drivers are short-circuit current limited and are protect-

ed against excessive power dissipation by thermal

shutdown circuitry that places the driver outputs into a

high-impedance state. The receiver input has a fail-safe

feature that guarantees a logic-high output if the input

is open circuit.

and outputs meet RS-485/RS-422 specifications.

________________________Applications

Isolated RS-485/RS-422 Data Interface

Transceivers for EMI-Sensitive Applications

Industrial-Control Local Area Networks

Automatic Test Equipment

HVAC/Building Control Networks

____________________________Features

o Slew-Rate-Limited Data Transmission (MAX3480B)

o High-Speed, Isolated, 2.5Mbps RS-485 Interface

(MAX3480A)

o -7V to +12V Common-Mode Input Voltage Range

with Respect to Isolated Ground

o Single +3.3V Supply

o Current Limiting and Thermal Shutdown for

Driver Overload Protection

o Standard 28-Pin DIP Package

Complete, Isolated, 3.3V

RS-485/RS-422 Data Interface

________________________________________________________________

Maxim Integrated Products

1

28

27

26

25

24

23

22

21

1

2

3

4

5

6

7

8

AC1

AC2

B

D2

D1

ISO RO DRV

A

ISO DI IN

ISO DE IN

SD

FS

GND1

20

19

18

17

9

10

11

12

ISO COM1

ISO DI DRV

ISO DE DRV

GND2

DE

DI

16

15

13

14

ISO COM2

ISO RO LED

RO

MAX485

MAX487

MAX845

ISOLATION BARRIER

TOP VIEW

MAX3480A/B

DIP

__________________Pin Configuration

19-0453; Rev 0; 1/96

PART

MAX3480ACPI

MAX3480AEPI

MAX3480BCPI

0°C to +70°C

-40°C to +85°C

0°C to +70°C

TEMP. RANGE

PIN-PACKAGE

28 Plastic DIP

28 Plastic DIP

28 Plastic DIP

MAX3480BEPI

-40°C to +85°C

28 Plastic DIP

DATA

RATE

(kbps)

2500

2500

250

250

______________Ordering Information