PIN DESCRIPTION

Mnemonic

Function

V

DD

Power Supply Input, 5 V

± 5%.

GND

Ground Pin. Must be connected to 0 V.

A+ . . . H+

Noninverting Input to Differential Receivers

A to H.

A– . . . H–

Inverting Input to Differential Receivers A to H.

A

Receiver Outputs A to H.

A through D and FS2 controls receivers

E through H.

FS1, FS2

Failsafe Control Inputs. FS1 controls receivers

A through D and FS2 control Receiver

E through H.

REV. 0

–4–

ADM5180

PIN CONFIGURATIONS

DIP

A–

A+

B+

FS1

G+

G–

B–

H+

H–

C–

FS2

C+

F+

D–

F–

D+

E+

GND

E–

13

18

1

2

28

27

5

6

7

24

23

22

3

4

26

25

8

21

9

20

10

19

11

11

12

17

16

14

15

TOP VIEW

(Not to Scale)

ADM5180

PLCC

H–

FS2

F+

G+

G–

B+

C+

D–

FS1

C–

26

27

28

4

2

3

15

18

17

16

12

14

13

25

24

21

20

19

23

22

TOP VIEW

(Not to Scale)

1

5

6

9

10

11

7

8

ADM5180

APPLICATIONS INFORMATION

FAILSAFE OPERATION

The ADM5180 provides a failsafe operating mode to guard against

input fault conditions as defined in RS-422A and RS-423A

standards. The fault conditions are (1) Driver in power-off

condition, (2) Receiver not interconnected with Driver, (3) Open-

circuited interconnecting cable, and (4) Short-circuited intercon-

necting cable. If any of these four fault conditions occurs at the

inputs of a receiver, then the output of that receiver is driven to a

known logic level. The failsafe level is programmed using the

failsafe (FS) input. There are two failsafe inputs, FS1 and FS2

which each control four receivers. FSI controls receivers A ...D

and FS2 controls receivers E . . . H. A connection to V

failsafe input sets the output high under fault conditions while a

connection to GND sets the output low.

FS1, FS2

Output During Fault Condition

V

DD

High

GND

Low

Input Filtering

The ADM5180 contains internal low pass filtering for additional

noise rejection. Frequencies above the passband will be rejected.

For the specified input (5.5 MHz at

±500 mV) the input stage

attenuates the signal such that the threshold levels are not reached

and therefore no change of state occurs on the output. The filtering

is a function of both amplitude and and frequency. As the signal

amplitude decreases then the rejected frequency will decrease.