LT1341CSW 查看數據表（PDF） - Linear Technology

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LT1341CSW

5V RS232 Transceiver with One Receiver Active in Shutdown

Linear Technology 

LT1341

PI FU CTIO S

V–: Negative Supply Output (RS232 Drivers). V – ≈

–(2VCC – 2.5V). This pin requires an external charge

storage capacitor C ≥ 0.1µF. To reduce supply ripple,

increase the size of the storage capacitor. With multiple

transceivers, the V + and V – pins may be paralleled into

common filter capacitors.

C1+, C1–, C2+, C2–: Commutating Capacitor Inputs. These

pins require two external capacitors C ≥ 0.2µF: one from

C1+ to C1–, and another from C2+ to C2–. The capacitor’s

effective series resistance should be less than 2Ω. 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.

Connect the 12V supply to C1+ and V +. The 12V supply

should be decoupled with a 0.1µF ceramic capacitor.

DRIVER IN: RS232 Driver Input Pins. These inputs are

TTL/CMOS compatible. Tie unused inputs to VCC.

DRIVER OUT: Driver Outputs at RS232 Voltage Levels.

Outputs are in a high impedance state when in shut-

down mode, VCC = 0V, or when the DRIVER DISABLE

pin is active. Outputs are fully short-circuit protected

from VOUT = V – + 30V to VOUT = V+ – 30V. Applying

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

or VCC with the power on, off, or in shutdown mode.

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

special receiver remains active when the part is in shut-

down mode, consuming typically 60µA. 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.

U

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

charge storage. ESD testing must be done with pins VCC,

V+, V – and GND shorted to ground or connected with low

ESR capacitors.

0.1µF

RS232

LINE PINS

PROTECTED

TO ±10kV

ESD Test Circuit

V+ 1

5V VCC 2

0.1µF

3

0.2µF

4

5

DRIVER 1 OUT

6

RX1 IN

DRIVER 2 OUT 7

8

RX2 IN

9

RX3 IN

10

RX4 IN

DRIVER 3 OUT 11

12

RX5 IN (LOW-Q)

13

ON/OFF

NC 14

LT1341

28 V–

27

0.1µF

26

0.2µF

25 DRIVER 1 IN

24

RX1 OUT

23

DRIVER 2 IN

22 RX2 OUT

21 RX3 OUT

20

RX4 OUT

19

DRIVER 3 IN

18 RX5 OUT (LOW-Q)

17

GND

16

DRIVER DISABLE

15

NC

LT1341 • ESD TC

6

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