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LTC1348

3.3V/5V Low Power RS232

3-Driver/5-Receiver Transceiver

ESCRIPTIO

■

Low Supply Current: 600µA at 3.3V

■

Supply Current in Shutdown: 0.2µA

■

Supply Current in Receiver Alive Mode: 15µA

■

ESD Protection over ±10kV

■

Operates from a Single 3V to 5.5V Supply

■

Operates to 120kBaud with 0.1µF Flying Capacitors

■

Three-State Outputs Are High Impedance When Off

■

Output Overvoltage Does Not Force Current

Back into Supplies

■

RS232 I/O Lines Can Be Forced to ±25V

Without Damage

■

Flowthrough Architecture

The LTC

1348 is a 3-driver/5-receiver RS232 transceiver

with very low supply current. The charge pump only

requires five 0.1µF capacitors. The LTC1348 provides full

RS232 output levels when operated over a wide supply

range of 3V to 5.5V

The transceiver operates in one of four modes: Normal,

Receiver Disable, Receiver Alive and Shutdown. In Normal

or Receiver Disable mode, I

is only 600µA at 3.3V and

800µA at 5V in the no load condition. In Shutdown mode,

the supply current is further reduced to 0.2µA. In Receiver

Alive mode, all five receivers are kept alive and the supply

current is 15µA. All RS232 outputs assume a high imped-

ance state in Shutdown or Receiver Alive mode or with the

power off. The receiver outputs assume a high impedance

state in Receiver Disable or with the power off.

The LTC1348 is fully compliant with all data rate and

overvoltage RS232 specifications. The transceiver oper-

ates up to 120kbaud with all drivers loaded with 1000pF,

3kΩ. Both driver outputs and receiver inputs can be forced

to ±25V without damage and can survive multiple ±10kV

ESD strikes.

■

Notebook Computers

■

Palmtop Computers

■

Printers

■

Portable Instruments

LT1348 • TA01

C5

0.1µF



C2

0.1µF

C3

0.1µF

C4

0.1µF

LTC1348

1

2

3

4

5

6

7

8

9

10

11

12

13

DR 1 OUT

RX1 IN

DR 2 OUT

RX2 IN

RX3 IN

RX4 IN

DR 3 OUT

RX5 IN



28

27

26

25

24

23

22

21

20

19

18

17

16

DR 1 IN

RX1 OUT

DR 2 IN

RX2 OUT

RX3 OUT

RX4 OUT

DR 3 IN

RX5 OUT

DREN

RXEN



–

GND

C1

0.1µF

3-Drivers/5-Receivers with Shutdown

ITY

Supply Current

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

TEMPERATURE (˚C)

–40

SUPPLY CURRENT (mA)

1.4

LT1348 •TA02

0.8

0.4

–20 0 40

0.2

1.6

1.2

1.0

0.6

SHUTDOWN CURRENT (µA)

1.4

0.8

0.4

0.2

1.6

1.2

1.0

0.6

60 80

QUIESCENT

CURRENT

SHUTDOWN

CURRENT

= 5V

= 3.3V

= 3.3V

OR 5V

Summary of content (8 pages)

PAGE 1
LTC1348 3.3V/5V Low Power RS232 3-Driver/5-Receiver Transceiver U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Low Supply Current: 600µA at 3.3V Supply Current in Shutdown: 0.2µA Supply Current in Receiver Alive Mode: 15µA ESD Protection over ±10kV Operates from a Single 3V to 5.5V Supply Operates to 120kBaud with 0.
PAGE 2
LTC1348 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltage (VCC) ................................................ 6V Input Voltage Driver ....................................... – 0.3V to V CC + 0.3V Receiver ............................................... – 25V to 25V Driver/Receiver Enable Pin ........ – 0.3V to VCC + 0.3V Output Voltage Driver ................................................... – 25V to 25V Receiver .................................... – 0.
PAGE 3
LTC1348 DC ELECTRICAL CHARACTERISTICS VCC = 3V to 5.5V, C1 to C4 = 0.1µF, unless otherwise noted. PARAMETER Power Supply Generator V + Output Voltage V – Output Voltage Supply Rise Time Power Supply VCC Supply Current Supply Leakage Current (VCC) Driver/Receiver Enable Threshold Low Driver/Receiver Enable Threshold High Driver/Receiver Enable Threshold High CONDITIONS MIN IOUT = 0mA IOUT = 8mA IOUT = 0mA IOUT = – 8mA Shutdown to Turn-On TYP MAX 8.0 7.5 – 8.0 – 7.0 0.2 No Load (Note 2) VCC = 3.
PAGE 4
LTC1348 U W TYPICAL PERFORMANCE CHARACTERISTICS 120kbps 250kbps 64kbps OUTPUT HIGH 20kbps VCC = 3.3V 0.1µF FLYING CAPACITORS ALL DRIVERS LOADED 3kΩ + CL 1 DRIVER DRIVEN OUTPUT LOW 64kbps 20kbps 120kbps 250kbps 0 3000 4000 1000 2000 LOAD CAPACITANCE (pF) 50 7 6 5 4 3 2 1 0 –1 –2 –3 –4 –5 –6 –7 120kbps VCC = 3.3V 0.1µF FLYING CAPACITORS ALL DRIVERS DRIVEN AND LOADED 3kΩ + CL OUTPUT LOW 3000 4000 1000 2000 LOAD CAPACITANCE (pF) 10 VCC = 3V 40 50 20 30 TEMPERATURE (°C) 60 45 VCC = 3.
PAGE 5
LTC1348 U U U PI FU CTIO S VCC: 3V to 5.5V Input Supply Pin. This pin should be decoupled with a 0.1µF ceramic capacitor. efficiency, the capacitor’s effective series resistance should be less than 1Ω. Ceramic capacitors are recommended. GND: Ground Pin. DR IN: RS232 Driver Input Pins. Inputs are TTL/CMOS compatible. The inputs of unused drivers can be left unconnected since 300k input pull-up resistors to VCC are included on chip.
PAGE 6
LTC1348 U W W SWITCHI G TI E WAVEFOR S DRIVER INPUT VCC 1.4V 1.4V 0V V+ DRIVER OUTPUT 0V 0V t LHD V– VCC 1.7V RX INPUT RX OUTPUT 1.3V 2.4V 0.8V t LHR t HLD 0V t HLR LTC1348 • F01 VCC 0V LTC1348 • F02 Figure 1. Driver Propagation Delay Timing Figure 2. Receiver Propagation Delay Timing TEST CIRCUITS ESD Test Circuit DRIVER OUTPUT DRIVER INPUT DRIVER V+ 51pF 3k 0.1µF 0.
PAGE 7
LTC1348 U U W U APPLICATIONS INFORMATION High Data Rates The LTC1348 maintains true RS232 ±5V minimum driver output even at high data rates. Figure 5 shows a test circuit with 2m wires connecting the two test chips. Both chips are run from 3.3V supplies. Figure 6 shows the typical line waveforms with all three drivers, loaded with 1000pF and 3kΩ, toggling simultaneously at 120kbaud. Figure 7 shows V+ 1 + C2 2 0.1µF 3 0.
PAGE 8
LTC1348 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. G Package 28-Lead Plastic SSOP (0.209) (LTC DWG # 05-08-1640) 0.205 – 0.212** (5.20 – 5.38) 0.397 – 0.407* (10.07 – 10.33) 28 27 26 25 24 23 22 21 20 19 18 17 16 15 0.068 – 0.078 (1.73 – 1.99) 0° – 8° 0.005 – 0.009 (0.13 – 0.22) 0.0256 (0.65) BSC 0.022 – 0.037 (0.55 – 0.95) *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH.