6

LT1341

PI FU CTIO S

≈

storage capacitor C

≥ 0.1µF. To reduce supply ripple,

increase the size of the storage capacitor. With multiple

common filter capacitors.

pins require two external capacitors C

≥ 0.2µF: one from

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 compli-

ance. When a 12V supply is available, C1 may be omitted.

should be decoupled with a 0.1

µF ceramic capacitor.

DRIVER IN: RS232 Driver Input Pins. These inputs are

DRIVER OUT: Driver Outputs at RS232 Voltage Levels.

Outputs are in a high impedance state when in shut-

pin is active. Outputs are fully short-circuit protected

higher voltages will not damage the device if the over-

drive 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.

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, including

LOW-Q RX OUT, are fully short-circuit protected to ground

LOW Q-CURRENT RX IN: Low Power Receiver Input. This

special receiver remains active when the part is in shut-

down mode, consuming typically 60

µA. This receiver has

the same input and protection characteristics as the other

receivers.

LOW Q-CURRENT RX OUT: Low Power Receiver Output.

This pin produces the same TTL/CMOS output voltage

levels with slightly decreased speed and short-circuit

current.

ESD PROTECTIO

The RS232 line inputs of the LT1341 have on-chip protec-

tion 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

LT1341 must be connected to ground through low imped-

ances. 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.

ESD Test Circuit

LT1341 • ESD TC

0.1

µF

0.2

µF

0.1

µF

RS232

LINE PINS

PROTECTED

TO

±10kV

LT1341

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 (LOW-Q)

ON/OFF

NC

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 (LOW-Q)

0.1

µF

GND

DRIVER DISABLE

NC