__________Applications Information

The MAX481/MAX483/MAX485/MAX487–MAX491 and

MAX1487 are low-power transceivers for RS-485 and RS-

422 communications. The MAX481, MAX485, MAX490,

MAX491, and MAX1487 can transmit and receive at data

rates up to 2.5Mbps, while the MAX483, MAX487,

MAX488, and MAX489 are specified for data rates up to

250kbps. The MAX488–MAX491 are full-duplex trans-

ceivers while the MAX481, MAX483, MAX485, MAX487,

and MAX1487 are half-duplex. In addition, Driver Enable

(DE) and Receiver Enable (RE) pins are included on the

MAX481, MAX483, MAX485, MAX487, MAX489,

MAX491, and MAX1487. When disabled, the driver and

receiver outputs are high impedance.

MAX487/MAX1487:

128 Transceivers on the Bus

The 48k

Ω

MAX487 and MAX1487 allows up to 128 transceivers

on a bus, compared to the 1-unit load (12k

Ω

input

impedance) of standard RS-485 drivers (32 trans-

ceivers maximum). Any combination of MAX487/

MAX1487 and other RS-485 transceivers with a total of

32 unit loads or less can be put on the bus. The

MAX481/MAX483/MAX485 and MAX488–MAX491 have

standard 12k

Ω

Receiver Input impedance.

Low-Power, Slew-Rate-Limited

RS-485/RS-422 Transceivers

8 _______________________________________________________________________________________

MAX488

MAX490

TOP VIEW

1

2

3

4

RO

DI

GND

8

7

6

5

A

B

Z

Y

DIP/SO

R

D

Rt

Rt

5

6

7

8

RO

DI

GND

4

GND

DI

RO

3

2

A

B

Y

Z

D

R

R

D

1

3

4

RO

2

A

1

6

5

7

8

GND

DI

Y

Z

B

µMAX

MAX488

MAX490

NOTE: TYPICAL OPERATING CIRCUIT SHOWN WITH DIP/SO PACKAGE.

MAX489

MAX491

DIP/SO

TOP VIEW

Rt

Rt

DE

RE GND

GND

DE

RO

DI

9

10

12

11

B

A

Z

Y

5

RO

NC

DI

2

1, 8, 13

3

6, 7

14

4

1

2

3

4

5

6

7

14

13

12

11

10

9

8

N.C.

N.C.

A

B

Z

Y

N.C.

RO

RE

DE

DI

GND

GND

R

D

D

R

D

R

Figure 2. MAX488/MAX490 Pin Configuration and Typical Operating Circuit

Figure 3. MAX489/MAX491 Pin Configuration and Typical Operating Circuit

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