Datasheet

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LTC1690

Differential Driver and

Receiver Pair with Fail-Safe

Receiver Output

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

The LTC

1690 is a low power receiver/driver pair that is

compatible with the requirements of RS485 and RS422.

The receiver offers a fail-safe feature that guarantees a

high receiver output state when the inputs are left open,

shorted together or terminated with no signal present. No

external components are required to ensure the high

receiver output state.

Separate driver output and receiver input pins allow full

duplex operation. Excessive power dissipation caused by

bus contention or faults is prevented by a thermal shut-

down circuit which forces the driver outputs into a high

impedance state.

The LTC1690 is fully specified over the commercial and

industrial temperature ranges. The LTC1690 is available in

8-Pin SO, MSOP and PDIP packages.

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Battery-Powered RS485/RS422 Applications

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Low Power RS485/RS422 Transceiver

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Level Translator

■

Line Repeater

120Ω

R2DRIVER

LTC1690 LTC1690

RECEIVER

120Ω

D2RECEIVER DRIVER

1690 TA01

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No Damage or Latchup to

15kV ESD (Human Body

Model), IEC1000-4-2 Level 4 (

8kV) Contact and

Level 3 (

8kV) Air Discharge

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Guaranteed High Receiver Output State for

Floating, Shorted or Terminated Inputs with No

Signal Present

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Drives Low Cost Residential Telephone Wires

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= 600µA Max with No Load

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Single 5V Supply

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

Ground Difference Between Devices on the Data Line

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Power-Up/Down Glitch-Free Driver Outputs Permit

Live Insertion or Removal of Transceiver

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Driver Maintains High Impedance with the Power Off

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Up to 32 Transceivers on the Bus

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Pin Compatible with the SN75179 and LTC490

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Available in SO, MSOP and PDIP Packages

1690 TA01a

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO

Driving a 1000 Foot STP Cable

Summary of content (12 pages)

PAGE 1
LTC1690 Differential Driver and Receiver Pair with Fail-Safe Receiver Output U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ No Damage or Latchup to ±15kV ESD (Human Body Model), IEC1000-4-2 Level 4 (±8kV) Contact and Level 3 (± 8kV) Air Discharge Guaranteed High Receiver Output State for Floating, Shorted or Terminated Inputs with No Signal Present Drives Low Cost Residential Telephone Wires ICC = 600µA Max with No Load Single 5V Supply –7V to 12V Common Mode Range Permits ±7V Ground Difference Between
PAGE 2
LTC1690 W W U W ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage (VCC) .............................................. 6.5V Driver Input Voltage ..................... –0.3V to (VCC + 0.3V) Driver Output Voltages ................................. –7V to 10V Receiver Input Voltages ......................................... ±14V Receiver Output Voltage .............. –0.3V to (VCC + 0.3V) Junction Temperature ........................................... 125°C Operating Temperature Range LTC1690C .........
PAGE 3
LTC1690 DC ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
PAGE 4
LTC1690 U W TYPICAL PERFOR A CE CHARACTERISTICS Receiver Input Offset Voltage vs Temperature Receiver Input Threshold Voltage vs Supply Voltage VCC = 5V –40 VCM = 0V –60 VCM = –7V –80 –100 –120 –140 VCM = 12V –160 –180 –200 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) –40 –25 TA = 25°C –60 OUTPUT HIGH –80 –100 OUTPUT LOW –120 –140 –160 4.5 25 20 15 10 5 4.6 4.4 4.2 4.0 3.8 3.6 3.4 3.2 3.
PAGE 5
LTC1690 U W TYPICAL PERFOR A CE CHARACTERISTICS Receiver Short-Circuit Current vs Temperature 1.75 320 300 OUTPUT LOW 40 30 OUTPUT HIGH 20 280 VCC = 5.25V 260 240 220 VCC = 4.75V 200 180 VCC = 5V 160 10 140 0 –55 –35 –15 120 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) 1690 G13 2.7 VCC = 5.25V VCC = 5V 2.3 2.1 1.9 VCC = 4.5V 1.7 VCC = 4.75V 1.5 –55 –35 –15 5 25 45 65 85 105 125 TEMPERATURE (°C) 2.9 2.7 RL = 54Ω VCC = 5.25V VCC = 5V 2.5 2.3 2.1 VCC = 4.5V 1.9 VCC = 4.75V 1.
PAGE 6
LTC1690 U W TYPICAL PERFOR A CE CHARACTERISTICS Driver Differential Output Voltage vs Output Current Driver Output High Voltage vs Output Current 100 –100 100 TA = 25°C VCC = 5V TA = 25°C 90 80 60 50 40 30 OUTPUT CURRENT (mA) OUTPUT CURRENT (mA) 70 –60 –40 20 60 50 40 30 10 0 0 0 1 2 3 4 5 DRIVER DIFFERENTIAL OUTPUT VOLTAGE (V) 0 0 0 1 2 3 4 DRIVER OUTPUT HIGH VOLTAGE (V) Driver Propagation Delay vs Temperature Driver Propagation Delay vs Supply Voltage 30 4.0 3.
PAGE 7
LTC1690 U U U PIN FUNCTIONS VCC (Pin 1): Positive Supply. 4.75V < VCC < 5.25V. Y (Pin 5): Driver Output. R (Pin 2): Receiver Output. R is high if (A – B) ≥ – 10mV and low if (A – B) ≤ – 200mV. Z (Pin 6): Driver Output. D (Pin 3): Driver Input. If D is high, Y is taken high and Z is taken low. If D is low, Y is taken low and Z is taken high. A (Pin 8): Receiver Input. B (Pin 7): Receiver Input. GND (Pin 4): Ground.
PAGE 8
LTC1690 U U W U APPLICATIONS INFORMATION A typical application is shown in Figure 6. Two twisted pair wires connect two driver/receiver pairs for full duplex data transmission. Note that the driver and receiver outputs are always enabled. If the outputs must be disabled, use the LTC491. There are no restrictions on where the chips are connected, and it isn’t necessary to have the chips connected to the ends of the wire.
PAGE 9
LTC1690 U U W U APPLICATIONS INFORMATION Fault Protection When shorted to –7V or 10V at room temperature, the short-circuit current in the driver outputs is limited by internal resistance or protection circuitry to 250mA maximum. Over the industrial temperature range, the absolute maximum positive voltage at any driver output should be limited to 10V to avoid damage to the driver outputs.
PAGE 10
LTC1690 U W U U APPLICATIONS INFORMATION Cables and Data Rate ESD PROTECTION The transmission line of choice for RS485 applications is a twisted pair. There are coaxial cables (twinaxial) made for this purpose that contain straight pairs, but these are less flexible, more bulky and more costly than twisted pairs. Many cable manufacturers offer a broad range of 120Ω cables designed for RS485 applications.
PAGE 11
LTC1690 U PACKAGE DESCRIPTION Dimensions in inches (millimeters) unless otherwise noted. MS8 Package 8-Lead Plastic MSOP (LTC DWG # 05-08-1660) 0.040 ± 0.006 (1.02 ± 0.15) 0.007 (0.18) 0.118 ± 0.004* (3.00 ± 0.102) 0.034 ± 0.004 (0.86 ± 0.102) 8 7 6 5 0° – 6° TYP SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) BSC 0.021 ± 0.006 (0.53 ± 0.015) 0.006 ± 0.004 (0.15 ± 0.102) 0.118 ± 0.004** (3.00 ± 0.102) 0.193 ± 0.006 (4.90 ± 0.
PAGE 12
LTC1690 U TYPICAL APPLICATIONS Receiver with Low Fail-Safe Output RS232 Receiver 5V 1.2k 2.7k RS232 IN 120Ω RECEIVER 2.7k RX RX RECEIVER 1.2k 1690 TA03 1690 TA02 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC485 5V Low Power RS485 Interface Transceiver Low Power LTC1480 3.