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LTC1483

sn1483 1483fs

Ultra-Low Power RS485 Low EMI

Transceiver with Shutdown

ESCRIPTIO

The LTC

1483 is an ultra-low power differential line trans-

ceiver designed for data transmission standard RS485

applications with extended common-mode range (–7V to

12V). It will also meet the requirements of RS422. The

LTC1483 features output drivers with controlled slew rate,

decreasing the EMI radiated from the RS485 lines, and

improving signal fidelity with misterminated lines. The

CMOS design offers significant power savings over its

bipolar counterparts without sacrificing ruggedness against

overload or ESD damage. Typical quiescent current is only

80µA while operating and less than 1µA in shutdown.

The driver and receiver feature three-state outputs, with

the driver outputs maintaining high impedance over the

entire common-mode range. Excessive power dissipation

caused by bus contention or faults is prevented by a

thermal shutdown circuit which forces the driver outputs

into a high impedance state. The receiver has a fail-safe

feature which guarantees a high output state when the

inputs are left open. I/O pins are protected against multiple

ESD strikes of over ±10kV.

The LTC1483 is fully specified over the commercial and

extended industrial temperature range and is available in

8-pin DIP and SO packages.

■

Low Power: I

= 120µA Max with Driver Disabled

■

= 500µA Max with Driver Enabled, No Load

■

1µA Quiescent Current in Shutdown Mode

■

Controlled Slew Rate Driver for Reduced EMI

■

Single 5V Supply

■

Drivers/Receivers Have ±10kV ESD Protection

■

–7V to 12V Common-Mode Range Permits ±7V

Ground Difference Between Devices on the Data Line

■

Thermal Shutdown Protection

■

Power Up/Down Glitch-Free Driver Outputs Permit

Live Insertion or Removal of Transceiver

■

Driver Maintains High Impedance in Three-State

or with the Power Off

■

Up to 32 Transceivers on the Bus

■

Pin Compatible with the LTC485

■

Battery-Powered RS485/RS422 Applications

■

Low Power RS485/RS422 Transceiver

■

Level Translator

ITY

CC1

GND1

RO1

RE1

DE1

DI1

CC2

GND2

RO2

RE2

DE2

DI2

TERM

LTC1483 • TA01

A – B

1483 TA02

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

Summary of content (8 pages)

PAGE 1
LTC1483 Ultra-Low Power RS485 Low EMI Transceiver with Shutdown U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Low Power: ICC = 120µA Max with Driver Disabled ICC = 500µA Max with Driver Enabled, No Load 1µA Quiescent Current in Shutdown Mode Controlled Slew Rate Driver for Reduced EMI Single 5V Supply Drivers/Receivers Have ±10kV ESD Protection – 7V to 12V Common-Mode Range Permits ±7V Ground Difference Between Devices on the Data Line Thermal Shutdown Protection Power Up/Down Glitch-Free Driver Outpu
PAGE 2
LTC1483 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltage (VCC) .............................................. 12V Control Input Voltage ..................... – 0.5V to VCC + 0.5V Driver Input Voltage ....................... – 0.5V to VCC + 0.5V Driver Output Voltage ........................................... ±14V Receiver Input Voltage .......................................... ±14V Receiver Output Voltage ................ – 0.5V to VCC + 0.
PAGE 3
LTC1483 U SWITCHI G CHARACTERISTICS VCC = 5V, (Notes 2, 3) unless otherwise noted.
PAGE 4
LTC1483 U W TYPICAL PERFORMANCE CHARACTERISTICS Driver Differential Output Voltage vs Temperature Driver Output Low Voltage vs Output Current 70 2.5 0 TA = 25°C RL = 54Ω 2.4 2.1 2.0 1.9 1.8 1.7 OUTPUT CURRENT (mA) 2.2 50 40 30 20 10 0 –25 50 0 75 25 TEMPERATURE (°C) 100 0 125 –20 –30 –40 –50 –60 –70 –80 1.6 1.5 –50 TA = 25°C –10 60 2.
PAGE 5
LTC1483 TEST CIRCUITS A 1k VCC VOD R S1 TEST POINT RECEIVER OUTPUT R VOC 1k CRL S2 B LTC1483 • F02 LTC1483 • F01 Figure 1. Driver DC Test Load Figure 2. Receiver Timing Test Load 3V DE A DI CL1 B CL2 S2 CL 15pF RE VCC 500Ω OUTPUT UNDER TEST RO RDIFF B S1 A LTC1483 • F04 LTC1483 • F03 Figure 3. Driver/Receiver Timing Test Circuit Figure 4. Driver Timing Test Load U W W SWITCHI G TI E WAVEFOR S 3V tr ≤ 10ns, tf ≤ 10ns 1.5V DI 1.
PAGE 6
LTC1483 U W W SWITCHI G TI E WAVEFOR S VOH 1.5V RO VOL tr ≤ 10ns, tf ≤ 10ns t PHL VOD2 A–B –VOD2 1.5V OUTPUT 0V t PLH 0V INPUT LTC1483 • F07 Figure 7. Receiver Propagation Delays 3V 1.5V RE 1.5V tr ≤ 10ns, tf ≤ 10ns 0V t ZL(SHDN), tZL 5V RO RO t LZ 1.5V OUTPUT NORMALLY LOW 0.5V 1.5V OUTPUT NORMALLY HIGH 0.5V 0V t HZ t ZH(SHDN), tZH LTC1483 • F08 Figure 8.
PAGE 7
LTC1483 U U W U APPLICATIO S I FOR ATIO The LTC1483 output stage will maintain a high impedance state until the breakdown of the N-channel or P-channel is reached when going positive or negative respectively. The output will be clamped to either VCC or ground by a Zener voltage plus a Schottky diode drop, but this voltage is well beyond the RS485 operating range. An ESD cell protects output against multiple ±10kV human body model ESD strikes.
PAGE 8
LTC1483 U U W U APPLICATIO S I FOR ATIO Shutdown Mode Both the receiver output (RO) and the driver outputs (A, B) can be placed in three-state mode by bringing RE high and DE low respectively. In addition, the LTC1483 will enter shutdown mode when RE is high and DE is low. In shutdown the LTC1483 typically draws only 1µA of supply current. In order to guarantee that the part goes into shutdown, RE must be high and DE must be low for at least 600ns simultaneously.