6

LT1280A/LT1281A

ESD PROTECTIO

The RS232 line inputs of the LT1280A/LT1281A have on-

chip protection from ESD transients up to

±10kV. The

protection structures act to divert the static discharge

safely to system ground. In order for the ESD protection to

function effectively, the power supply and ground pins of

the circuit must be connected to ground through low

impedances. The power supply decoupling capacitors and

charge pump storage capacitors provide this low imped-

ance in normal application of the circuit. The only con-

straint is that low ESR capacitors must be used for

bypassing and charge storage. ESD testing must be done

connected with low ESR capacitors.

ESD Test Circuit

1280A ESD TC

0.1

µF

RS232

LINE PINS

PROTECTED

TO

±10kV

1

2

3

4

18

17

16

15

14

13

12

11

10

0.1

µF

0.1

µF

0.1

µF

NC

DR2 OUT

LT1280A

0.1

µF

ON/OFF

GND

DR1 OUT

RX1 IN

RX1 OUT

DR1 IN

DR2 IN

RS232

LINE PINS

PROTECTED

TO

±10kV

RX2 IN

RX2 OUT

+

+

+

+

+

5

6

7

8

9

APPLICATI

TYPICAL

Supporting an LT1039 (Triple Driver/Receiver)

30k

30k

RS232 OUTPUT

RS232 OUTPUT

RS232 INPUT

RS232 INPUT

LT1280A • TA04

LT1039

TTL INPUT

30k

RS232 INPUT

TTL INPUT

TTL INPUT

TTL OUTPUT

TTL OUTPUT

TTL OUTPUT

ON/OFF

RS232 OUTPUT

5k

RS232 OUTPUT

RS232 INPUT

LT1280A

TTL INPUT

5k

RS232 INPUT

TTL INPUT

TTL OUTPUT

TTL OUTPUT

ON/OFF

RS232 OUTPUT

1

µF

2

4

1

µF

5

6

3

7

18

17

1

µF

1

µF

GND

16

GND

10

1

9

18

17

5V

SHUTDOWN

11

12

13

10

15

14

9

8

12

14

16

11

13

15

7

5

3

8

6

4

+

+

+