Datasheet

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LT1080/LT1081

10801fe

Advanced Low Power

5V RS232 Dual Driver/Receiver

The LT

1080/LT1081 are the only dual RS232 driver/

receiver with charge pump to guarantee absolutely no

latchup. These interface optimized devices provide a real-

istic balance between CMOS levels of power dissipation

and real world requirements for ruggedness. The driver

outputs are fully protected against overload and can be

shorted to ±30V. Unlike CMOS, the advanced architecture

of the LT1080/LT1081 does not load the signal line when

“shut down” or when power is off. Both the receiver and

RS232 outputs are put into a high impedance state. An

advanced output stage allows driving higher capacitive

loads at higher speeds with exceptional ruggedness

against ESD.

For applications requiring up to five drivers and five

receivers with charge pump in one package see the LT1130A

Series data sheet. A version of the LT1080/LT1081, the

LT1180A and LT1181A that use only 0.1µF capacitors, is

also available. All of Linear Technology’s RS232 ICs are

available in standard surface mount packages.

■

Superior to CMOS

– Improved Speed: Operates over 120kBaud

– Improved Protection: Outputs Can Be Forced

to ±30V without Damage

– Three-State Outputs Are High

Impedance When Off

– Only Needs 1µF Capacitors

■

Absolutely No Latchup

■

CMOS Comparable Low Power: 60mW

■

Can Power Additional RS232 Drivers: 10mA

■

Supply Current in Shutdown: 1µA

■

Available in SO Package

■

Available with or without Shutdown

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

■

Portable Computers

■

Battery-Powered RS232 Systems

■

Power Supply Generator

■

Terminals

■

Modems

Supply Generator Outputs

OUTPUT CURRENT (mA)

02468101214161820

OUTPUT VOLTAGE (V)

1080/81 TA01a

–2

–4

–6

–8

–10

= 5V

OUTPUT

TO V

–

TO GND

TO V

–

OUTPUT

LOGIC

INPUTS

LOGIC

OUTPUTS

ON/OFF

5V INPUT

9V OUTPUT

–9V OUTPUT

RS232 OUTPUT

RS232 INPUT

1080/81 • TA01

LT1080

1µF

FEATURES

DESCRIPTIO

APPLICATIO S

TYPICAL APPLICATIO

Summary of content (12 pages)

PAGE 1
LT1080/LT1081 Advanced Low Power 5V RS232 Dual Driver/Receiver U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ Superior to CMOS – Improved Speed: Operates over 120kBaud – Improved Protection: Outputs Can Be Forced to ±30V without Damage – Three-State Outputs Are High Impedance When Off – Only Needs 1µF Capacitors Absolutely No Latchup CMOS Comparable Low Power: 60mW Can Power Additional RS232 Drivers: 10mA Supply Current in Shutdown: 1µA Available in SO Package Available with or without Shutdown U APPLICATIO S ■
PAGE 2
LT1080/LT1081 W W W AXI U U ABSOLUTE RATI GS (Note 1) Supply Voltage (VCC) ................................................. 6V V + ........................................................................................... 12V V – ....................................................................................... –12V Input Voltage Driver ........................................................... V – to V + Receiver ................................................. –30V to 30V ON/OFF Pin ......
PAGE 3
LT1080/LT1081 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 2) PARAMETER CONDITIONS MIN TYP MAX UNITS ● ● 5 –5 7.3 –6.5 1.4 1.4 0.8 2 V V 5 5 20 20 µA µA Driver Output Voltage Swing Load = 3k to GND Both Outputs Positive Negative Logic Input Voltage Level Input Low Level (VOUT = High) Input High Level (VOUT = Low) ● ● Logic Input Current VIN ≥ 2V VIN ≤ 0.
PAGE 4
LT1080/LT1081 U U U PI FU CTIO S (Pin numbers refer to LT1080) C1+; C1–; C2+; C2 – (Pins 2, 4, 5, 6): Requires an external capacitor (≥1µF) from C1 + to C1 – and another from C2 + to C2 –. Pin 2 can be used for connecting a second positive supply. When a separate positive supply is used, C1 can be deleted. V + (Pin 3): Positive Supply for RS232 Drivers. V + ≈ 2VCC – 1.5V. Requires an exterenal capacitor (≥1µF) for charge storage. May be loaded (up to 15mA) for external system use.
PAGE 5
LT1080/LT1081 U W TYPICAL PERFOR A CE CHARACTERISTICS Receiver Output Short-Circuit Current Receiver Input Thresholds ON/OFF Pin Current vs Voltage 100 3.00 40 35 2.75 INPUT HIGH 2.00 1.75 1.50 INPUT LOW 1.25 INPUT CURRENT (µA) 2.25 30 OUTPUT SINKING OUTPUT CURRENT (mA) INPUT THRESHOLD (V) 2.50 10 OUTPUT SOURCING 1 20 15 10 5 1.00 0 0.75 –5 0.50 –55 –25 0 25 50 75 TEMPERATURE (°C) 100 0.
PAGE 6
LT1080/LT1081 U U W U APPLICATIO S I FOR ATIO The driver output stage of the LT1080 offers significantly improved protection over older bipolar and CMOS designs. In addition to current limiting, the driver output can be externally forced to ±30V with no damage or excessive current flow, and will not disrupt the supplies. Some drivers have diodes connected between the outputs and the supplies, so externally applied voltages can cause excessive supply voltage to develop.
PAGE 7
LT1080/LT1081 U U W U APPLICATIO S I FOR ATIO The generated driver supplies (V + and V –) may be used to power external circuitry such as other RS232 drivers or op amps. They should be loaded with care, since excessive loading can cause the generated supply voltages to drop, causing the RS232 driver output voltages to fall below RS232 requirements. See the graph “Supply Generator Outputs” for a comparison of generated supply voltage versus supply current.
PAGE 8
LT1080/LT1081 U PACKAGE DESCRIPTIO J Package 16-Lead CERDIP (Narrow .300 Inch, Hermetic) (Reference LTC DWG # 05-08-1110) CORNER LEADS OPTION (4 PLCS) 0.005 (0.127) MIN 0.023 – 0.045 (0.584 – 1.143) HALF LEAD OPTION 0.840 (21.336) MAX 16 15 14 12 13 11 10 9 0.220 – 0.310 (5.588 – 7.874) 0.025 (0.635) RAD TYP 0.045 – 0.068 (1.143 – 1.727) FULL LEAD OPTION 2 1 3 5 4 6 7 8 0.200 (5.080) MAX 0.300 BSC (0.762 BSC) 0.015 – 0.060 (0.380 – 1.520) 0.008 – 0.018 (0.203 – 0.
PAGE 9
LT1080/LT1081 U PACKAGE DESCRIPTIO N Package 16-Lead PDIP (Narrow .300 Inch) (Reference 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) 0.009 – 0.015 (0.229 – 0.381) ( 0.020 (0.508) MIN +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 ± 0.076) 0.100 (2.
PAGE 10
LT1080/LT1081 U PACKAGE DESCRIPTIO SW Package 16-Lead Plastic Small Outline (Wide .300 Inch) (Reference LTC DWG # 05-08-1620) 0.398 – 0.413* (10.109 – 10.490) 16 15 14 13 12 11 10 9 0.394 – 0.419 (10.007 – 10.643) NOTE 1 1 0.291 – 0.299** (7.391 – 7.595) 2 3 4 5 6 7 0.093 – 0.104 (2.362 – 2.642) 0.010 – 0.029 × 45° (0.254 – 0.737) 8 0.037 – 0.045 (0.940 – 1.143) 0° – 8° TYP 0.009 – 0.013 (0.229 – 0.330) NOTE 1 0.016 – 0.050 (0.406 – 1.270) 0.050 (1.270) BSC 0.004 – 0.012 (0.
PAGE 11
LT1080/LT1081 U PACKAGE DESCRIPTIO SW Package 18-Lead Plastic Small Outline (Wide .300 Inch) (Reference LTC DWG # 05-08-1620) 0.447 – 0.463* (11.354 – 11.760) 18 17 16 15 14 13 12 11 10 0.394 – 0.419 (10.007 – 10.643) NOTE 1 0.291 – 0.299** (7.391 – 7.595) 1 2 3 4 5 6 7 8 9 0.093 – 0.104 (2.362 – 2.642) 0.010 – 0.029 × 45° (0.254 – 0.737) 0.037 – 0.045 (0.940 – 1.143) 0° – 8° TYP 0.009 – 0.013 (0.229 – 0.330) NOTE 1 0.016 – 0.050 (0.406 – 1.270) 0.050 (1.270) BSC 0.004 – 0.
PAGE 12
LT1080/LT1081 U TYPICAL APPLICATIO Supporting an LT1039 (Triple Driver/Receiver) SHUTDOWN 5V 18 ON/OFF VCC LT1080 17 18 VCC 17 ON/OFF LT1039 TTL INPUT RS232 OUTPUT TTL INPUT RS232 OUTPUT TTL INPUT RS232 OUTPUT TTL INPUT RS232 OUTPUT TTL INPUT RS232 OUTPUT RS232 INPUT TTL OUTPUT RS232 INPUT TTL OUTPUT 5k 30k RS232 INPUT TTL OUTPUT *C1 1µF 2 C1+ 4 C1– 30k RS232 INPUT TTL OUTPUT 5 1µF RS232 INPUT TTL OUTPUT 5k 6 30k C2 + C2 – V+ 3 1 V+ V– 7 9 V– GND 16 GND 1µF