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LTC1480

3.3V Ultra-Low Power

RS485 Transceiver

ESCRIPTIO

The LTC

1480 is an ultra-low power differential line trans-

ceiver which provides full RS485 compatibility while oper-

ating from a single 3.3V supply. It is designed for data

transmission standard RS485 applications with extended

common-mode range (12V to –7V). It also meets the

requirements of RS422 and features high speed operation

up to 2.5Mb/s. The CMOS design offers significant power

savings without sacrificing ruggedness against overload

or ESD damage. Typical quiescent current is only 300µA

while operating and 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 up to ±10kV.

The LTC1480 is fully specified over the commercial and

extended industrial temperature range. The LTC1480 is

available in 8-pin SO and DIP packages.

■

True RS485 from a Single 3.3V Supply

■

Low Power: I

= 500µA Max with Driver Disabled

■

= 600

A Max with Driver Enabled, No Load

■

A Quiescent in Shutdown Mode

■

ESD Protection to

10kV on Receiver Inputs and

Driver Outputs

■

–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

■

50ns Typical Driver Propagation Delays with

10ns Skew

■

Pin Compatible with the LTC485

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

■

Battery-Powered RS485/RS422 Applications

■

Low Power RS485/RS422 Transceiver

■

Level Translator

ITY

Driver Differential

Output Voltage vs Output Current

3.3V RS485 Network

RO

RE

DE

1

2

3

8

7

6

LTC1480 • TA01

LTC1480

120Ω120Ω

SHIELD SHIELD

3.3V

RO

RE

DE

1

2

3

8

7

6

LTC1480

3.3V

1234

8765

RO RE DE D1

OUTPUT CURRENT (mA)

OUTPUT VOLTAGE (V)

0.5

1.0

1.5

2.0

2.5

60 70 80

LTC1480 • TA02

10 20 30 40 50 90

3.0

3.5

= 3.3V

= 25°C

Summary of content (9 pages)

PAGE 1
LTC1480 3.3V Ultra-Low Power RS485 Transceiver U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ True RS485 from a Single 3.
PAGE 2
LTC1480 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltage (VCC) ................................................ 7V Control Input Voltage ..................... – 0.3V to VCC + 0.3V Driver Input Voltage ....................... – 0.3V to VCC + 0.3V Driver Output Voltage ........................................... ±14V Receiver Input Voltage .......................................... ±14V Receiver Output Voltage ................ – 0.3V to VCC + 0.
PAGE 3
LTC1480 U SWITCHI G CHARACTERISTICS VCC = 3.
PAGE 4
LTC1480 U W TYPICAL PERFORMANCE CHARACTERISTICS Receiver Output Low Voltage vs Output Current Driver Skew vs Temperature 25 7.0 20 OUTPUT CURRENT (mA) 6.0 TIME (ns) – 16 VCC = 3.3V TA = 25°C VCC = 3.3V 5.5 5.0 4.5 4.0 – 14 OUTPUT CURRENT (mA) 6.5 Receiver Output High Voltage vs Output Current 15 10 – 12 – 10 5 3.5 –8 –6 –4 –2 3.0 – 40 – 20 0 0 40 60 20 TEMPERATURE (°C) 80 100 0 3.30 3.05 2.80 2.55 2.30 2.05 1.80 1.55 1.30 OUTPUT VOLTAGE (V) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.
PAGE 5
LTC1480 U U FU CTIO TABLES LTC1480 Receiving LTC1480 Transmitting INPUTS INPUTS OUTPUTS OUTPUTS RE DE DI B A RE DE A–B RO X 1 1 0 1 0 0 ≥ 0.2V 1 0 ≤ – 0.2V 0 X 1 0 1 0 0 0 0 X Z Z 0 0 Inputs Open 1 1 0 X Z* Z* 1 0 X Z* *Shutdown mode *Shutdown mode TEST CIRCUITS A VOD 1k VCC VOC R S1 TEST POINT RECEIVER OUTPUT R 1k CRL S2 B LTC1480 • F02 LTC1480 • F01 Figure 1. Driver DC Test Load Figure 2.
PAGE 6
LTC1480 U W W SWITCHI G TI E WAVEFOR S 3V f = 1MHz, tr ≤ 10ns, tf ≤ 10ns 1.5V DE 1.5V 0V t LZ t ZL(SHDN), t ZL 3.3V A, B VOL 2.3V OUTPUT NORMALLY LOW 0.5V 2.3V OUTPUT NORMALLY HIGH 0.5V VOH A, B 0V t HZ t ZH(SHDN), t ZH LTC1480 • F06 Figure 6. Driver Enable and Disable Times VOH 1.5V RO VOL f = 1MHz, tr ≤ 10ns, tf ≤ 10ns t PHL VOD2 A–B –VOD2 1.5V OUTPUT 0V t PLH 0V INPUT LTC1480 • F07 Figure 7. Receiver Propagation Delays 3V 1.5V RE 3.3V RO VOL t ZL(SHDN), tZL t LZ 1.
PAGE 7
LTC1480 U U W U APPLICATIO S I FOR ATIO voltage exceeds the supply rails. Latch-up at the output drivers is virtually eliminated and the driver is prevented from loading the line under RS485 specified fault conditions. A proprietary output protection structure protects the transceiver line terminals against ESD strikes of up to ±10kV. When two or more drivers are connected to the same transmission line, a potential condition exists whereby more than two drivers are simultaneously active.
PAGE 8
LTC1480 U U W U APPLICATIO S I FOR ATIO 100pF BR TTL IN t r, t f < 6ns D R R 100Ω RECEIVER OUT LTC1480 • F11 100pF Figure 11. Receiver Propagation Delay Test Circuit U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. N8 Package 8-Lead Plastic DIP 0.300 – 0.325 (7.620 – 8.255) 0.009 – 0.015 (0.229 – 0.381) ( +0.025 0.325 –0.015 8.255 +0.635 –0.381 ) 0.130 ± 0.005 (3.302 ± 0.127) 0.045 – 0.065 (1.143 – 1.651) 0.400* (10.160) MAX 0.065 (1.651) TYP 0.125 (3.
PAGE 9
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