7

LT1080/LT1081

APPLICATIO S I FOR ATIO

When driving CMOS logic from a receiver that will be used

in the SHUTDOWN mode and there is no other active

receiver on the line, a 51k resistor can be placed from the

receiver output is in a high impedance state.

power external circuitry such as other RS232 drivers or op

amps. They should be loaded with care, since excessive

loading can cause the generated supply voltages to drop,

causing the RS232 driver output voltages to fall below

RS232 requirements. See the graph “Supply Generator

Outputs” for a comparison of generated supply voltage

versus supply current.

1080/81 F08

DRIVER

3

EXTERNAL OP AMP

LT1080

7

1

µF

1

µF

–

+

GND

16

+

TYPICAL APPLICATIO

To protect against receiver input overloads in excess of

±30V, a voltage clamp can be placed on the data line and

still maintain RS232 compatibility.

RS232

INPUT

RECEIVER

LOGIC

OUTPUT

1080/81 F067

5k

1k*

30V

30V

* A PTC THERMISTOR WILL ALLOW

CONTINUOUS OVERLOAD OF GREATER THAN

±100V

Operating with 5V and 12V

LOGIC

INPUTS

LOGIC

OUTPUTS

ON/OFF

18

10

13

11

12

6

5

4

2

16

9

14

8

15

7

3

17

5V INPUT

12V INPUT*

–12V OUTPUT

RS232 OUTPUT

RS232 OUTPUT

RS232 INPUT

RS232 INPUT

1080/81 • TA03

5k

5k

LT1080

1

µF

1

µF

* PIN 1 USED ON LT1081.

1080/81 F06

RS232

INPUT

ON/OFF

INPUT

LT1080

RECEIVER

CMOS

LOGIC

LOGIC

OUTPUT

51k*