8

LT1130A/LT1140A Series

PI FU CTIO S

– 2.5V). This pin requires an external charge storage

capacitor C

30 seconds.

These pins require two external capacitors C

≥ 0.2µF: one

maintain charge pump efficiency, the capacitor’s effective

series resistance should be less than 2

Ω. For C ≥ 1µF, low

ESR tantalum capacitors work well in this application,

although small value ceramic capacitors may be used

with a minimal reduction in charge pump compliance. In

applications where larger positive voltages are available,

such as 12V, C1 may be omitted and the positive voltage

µF

ceramic capacitor.

DRIVER IN: RS232 Driver Input Pins. These inputs are

TTL/CMOS compatible. Inputs should not be allowed to

DRIVER OUT: Driver Outputs at RS232 Voltage Levels.

Driver output swing meets RS232 levels for loads up to 3k.

Slew rates are controlled for lightly loaded lines. Output

current capability is sufficient for load conditions up to

2500pF. Outputs are in a high impedance state when in

pin is active. Outputs are fully short-circuit protected from

damage the device if the overdrive is moderately current

limited. Short circuits on one output can load the power

supply generator and may disrupt the signal levels of the

other outputs. The driver outputs are protected against

ESD to

±10kV for human body model discharges.

RX IN: Receiver Inputs. These pins accept RS232 level

signals (

±30V) into a protected 5k terminating resistor.

The receiver inputs are protected against ESD to

±10kV 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 LT1130A/LT1140A series of

RS232 Driver/Receivers 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 LT1130A/LT1140A

must be connected to ground through low impedances.

The power supply decoupling capacitors and charge

pump storage capacitors provide this low impedance in

normal application of the circuit. The only constraint is

that low ESR capacitors must be used for bypassing and

ESR capacitors.

The ESD protection on the LT1133A, LT1137A and

LT1141A meets

±15kV air gap discharge and ±8kV con-

tact methods per IEC-1000-4-2.

LT1130A • ESD TC

0.1

µF

0.2

µF

0.1

µF

RS232

LINE PINS

PROTECTED

TO

±15kV

LT1137A

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

+

ESD Test Circuit