6

LT1537

PI FU CTIO S

RX IN: Receiver Inputs. These pins accept RS232 level

signals (

± 25V) into a protected 5k terminating resistor.

The receiver inputs are protected against ESD to

±5kV for

human body model discharges. Each receiver provides

0.4V of hysteresis for noise immunity. Open receiver

inputs assume a logic low state.

RX OUT: Receiver Outputs with TTL/CMOS Voltage Lev-

els. Outputs are in a high impedance state when in shut-

down mode to allow data line sharing. Outputs are fully

on, off, or in shutdown mode.

ESD PROTECTIO

The RS232 line inputs of the LT1537 have on-chip protec-

tion from ESD transients up to

±5kV during shutdown or

power ON state. 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 LT1537 must be connected to

ground through low impedances. The power supply

decoupling capacitors and charge pump storage capaci-

tors provide this low impedance in normal application of

the circuit. The only constraint is that low ESR capacitors

must be used for bypassing and charge storage. ESD

shorted to ground or connected with low ESR capacitors.

TYPICAL APPLICATIO S

LT1537 Driving Remote Powered LTC1382

LT1537

5.1V

ON/OFF = 5V

2

× 0.1µF

2

× 0.1µF

0.1

µF

0.1

µF

0.1

µF

0.1

µF

0.1

µF

0.1

µF

0.1

µF

DRIVER

RS232 OUTPUT

DRIVER

RECEIVER

RECEIVER

DRIVER

LOGIC

INPUT

LOGIC

OUTPUT

RECEIVER

RECEIVER

DRIVER

RS232 OUTPUT

LOGIC

OUTPUT

LOGIC

INPUT

THREE

RECEIVERS

NOT USED

ON/OFF = 5V

0.1

µF

LT1537 • TA03

DRIVER

+

+

+

+

+

+

ESD Test Circuit

LT1537 • ESD TC

0.1

µF

0.2

µF

0.1

µF

RS232

LINE PINS

PROTECTED

TO

±5kV

LT1537

1

2

3

4

5

6

7

8

9

10

11

12

13

14

DRIVER 1 OUT

RX1 IN

DRIVER 2 OUT

RX2 IN

RX3 IN

RX4 IN

DRIVER 3 OUT

RX5 IN

ON/OFF

28

27

26

25

24

23

22

21

20

19

18

17

16

15

0.2

µF

DRIVER 1 IN

RX1 OUT

DRIVER 2 IN

RX2 OUT

RX3 OUT

RX4 OUT

DRIVER 3 IN

RX5 OUT

+

+

+

0.1

µF

GND

DRIVER DISABLE