Datasheet

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LT1381

Low Power 5V RS232 Dual

Driver/Receiver with

0.1µF Capacitors

Output Waveforms

DRIVER

OUTPUT

= 3k

= 2500pF

RECEIVER

OUTPUT

= 50pF

INPUT

■

Portable Computers

■

Battery-Powered Systems

■

Power Supply Generator

■

Terminals

■

Modems

ITY

ESCRIPTIO

■

ESD Protection over ±10kV

■

Low Cost

■

Uses Small Capacitors: 0.1µF

■

CMOS Comparable Low Power: 40mW

■

Operates from a Single 5V Supply

■

120kBaud Operation for R

= 3k, C

= 2500pF

■

250kBaud Operation for R

= 3k, C

= 1000pF

■

Rugged Bipolar Design

■

Outputs Assume a High Impedance State When

Powered Down

■

Absolutely No Latchup

■

Available in Narrow SO Package

0.1µF

LOGIC

INPUTS

LOGIC

OUTPUTS

5V INPUT

OUT

–

OUT

RS232 OUTPUT

RS232 INPUT

LT1381 • TA01

LT1381

0.1µF

, LTC and LT are registered trademarks of Linear Technology Corporation.

TransZorb

is a registered trademark of General Instruments, GSI

The LT

1381 is a dual RS232 driver/receiver pair with

integral charge pump to generate RS232 voltage levels

from a single 5V supply. The circuit features rugged

bipolar design to provide operating fault tolerance and

ESD protection unmatched by competing CMOS designs.

Using only 0.1µF external capacitors, the circuit con-

sumes only 40mW of power and can operate to 120kbaud

even while driving heavy capacitive loads. New ESD struc-

tures on the chip allow the LT1381 to survive multiple

±10kV strikes, eliminating the need for costly TransZorbs

on the RS232 line pins. Driver outputs are protected from

overload and can be shorted to ground or up to ±25V

without damage. During power-off conditions, driver and

receiver outputs are in a high impedance state, allowing

line sharing.

LT1381 • TA02

Summary of content (8 pages)

PAGE 1
LT1381 Low Power 5V RS232 Dual Driver/Receiver with 0.1µF Capacitors U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ESD Protection over ±10kV Low Cost Uses Small Capacitors: 0.
PAGE 2
LT1381 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltage (VCC) ................................................ 6V V + ........................................................................ 13.2V V – ...................................................................... –13.2V Input Voltage Driver ........................................................... V – to V + Receiver ...............................................
PAGE 3
LT1381 ELECTRICAL CHARACTERISTICS PARAMETER (Note 2) CONDITIONS MIN TYP MAX UNITS Input Low Threshold (VOUT = High) Input High Threshold (VOUT = Low) 0.8 1.3 1.7 2.4 V V 0.4 1.0 V Receiver Input Voltage Thresholds Hysteresis 0.1 ● Input Resistance (Note 6) Output Voltage Output Low, IOUT = – 1.6mA Output High, IOUT = 160µA (VCC = 5V) Output Short-Circuit Current ● ● Sinking Current, VOUT = VCC Sourcing Current, VOUT = 0V Propagation Delay 3 5 7 0.4 3.5 0.2 4.
PAGE 4
LT1381 W U TYPICAL PERFOR A CE CHARACTERISTICS Supply Current vs Data Rate Receiver Input Threshold 3.00 100 2.50 SUPPLY CURRENT (mA) 40 2.25 INPUT HIGH 2.00 1.75 1.50 INPUT LOW 1.25 1.00 LEAKAGE CURRENT (µA) 2 DRIVERS ACTIVE RL = 3k CL = 2500pF 2.75 THRESHOLD VOLTAGE (V) Driver Leakage in Shutdown 50 30 20 10 VOUT = 30V 1 VOUT = –30V 10 0.75 0.50 –55 –25 50 25 0 75 TEMPERATURE (°C) 100 0 125 0 25 50 75 100 DATA RATE (kBaud) 125 LT1381 • TPC04 0.
PAGE 5
LT1381 U U U PI FU CTIO S C1 +, C1 –, C2 +, C2 – (Pins 1, 3, 4, 5): Commutating Capacitor Inputs. These pins require two external capacitors C ≥ 0.1µF: one from C1+ to C1– and another from C2+ to C2 –. C1 may be deleted if a separate 12V supply is available and connected to pin C1+. V + (Pin 2): Positive Supply Output (RS232 Drivers). V + ≈ 2VCC – 2.1V. This pin requires an external charge storage capacitor C ≥ 0.1µF, tied to ground or VCC. Larger value capacitors may be used to reduce supply ripple.
PAGE 6
LT1381 U TYPICAL APPLICATIO S Isolated RS232 Driver/Receiver CTX20-1 1:1 VIN = 5V ±10% FROM SYSTEM ILIM 100µF 1Ω VIN + 13.7V 10k + FB ISOLATOR OUTPUT (DATA TO SYSTEM) 1µF SW2 1k 16 VCC 1 VCC OS 10µF 1N5818 LT1111 VOUT 0.1µF 100µF SW1 GND 5V ±10% LT1121-5 + L1 20µH 47Ω + 1N5818 + IN 0.1µF 3 LTC1145 LT1381 RS232 2 + 4 GND2 GND1 0.1µF + 0.1µF 5 6 + ISOLATOR INPUT (DATA FROM SYSTEM) VIN 9 VCC IN RX OS LTC1145 GND1 11 DX 8 14 0.
PAGE 7
LT1381 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. N Package 16-Lead PDIP (Narrow 0.300) (LTC DWG # 05-08-1510) 0.770* (19.558) MAX 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 0.255 ± 0.015* (6.477 ± 0.381) 0.130 ± 0.005 (3.302 ± 0.127) 0.300 – 0.325 (7.620 – 8.255) 0.020 (0.508) MIN 0.009 – 0.015 (0.229 – 0.381) ( +0.035 0.325 –0.015 8.255 +0.889 –0.381 0.045 – 0.065 (1.143 – 1.651) ) 0.065 (1.651) TYP 0.125 (3.175) MIN 0.018 ± 0.003 (0.457 ± 0.
PAGE 8
LT1381 U TYPICAL APPLICATIO S Operation Using 5V and 12V Power Supplies 12V INPUT + 0.1µF LOGIC INPUTS 1 16 2 3 LT1381 4 5V INPUT 16 –12VOUT + 5 11 14 10 7 12 13 0.1µF RS232 OUTPUT RS232 OUTPUT RS232 INPUT 5k LOGIC OUTPUTS 9 8 S 5k RS232 INPUT 15 LT1381 • TA06 Sharing Capacitors 5V VCC TTL INPUT TTL INPUT TTL OUTPUT 16 V+ LT1381 V– 2 5V VCC 6 11 14 10 7 12 13 16 LT1381 + RS232 OUTPUT + RS232 OUTPUT RS232 INPUT 0.