75179

SN75179B Differential Driver and Receiver Pair

Overview

The SN75179B is a high-performance differential driver and receiver pair designed for balanced transmission-line applications. It complies with industry standards including TIA/EIA-422-B, TIA/EIA-485-A, and ITU Recommendation V.11. This component is optimized for full-duplex data communications over extended bus lines, ensuring reliable signal integrity in challenging environments.

The device integrates robust protection features such as driver current limiting and thermal shutdown, making it suitable for industrial applications where fault conditions may occur. The receiver section offers exceptional noise immunity through input hysteresis and maintains high input impedance across a wide common-mode voltage range.

Key Features

• Compliant with TIA/EIA-422-B, TIA/EIA-485-A, and ITU V.11 standards
• Designed for full-duplex balanced transmission line applications
• Driver features:
  • Positive and negative current limiting
  • Thermal shutdown protection (activates at ~150°C junction temperature)
  • 60 mA maximum drive capability
• Receiver features:
  • High input impedance
  • Input hysteresis for enhanced noise immunity
  • ±200 mV input sensitivity
  • Wide common-mode input range (-7V to +12V)
• Operating temperature range: 0°C to 70°C

Applications

The SN75179B is ideal for various data communication systems requiring robust differential signaling:

• RS-422/RS-485 communication networks
• Industrial control systems
• Telecommunications equipment
• Building automation systems
• Process control instrumentation
• Long-distance data transmission systems
• Multipoint bus transmission lines

Electrical Characteristics

Driver Section

• Supply Voltage Range: 4.75V to 5.25V
• Output Short-Circuit Current: 60 mA (max)
• Differential Output Voltage: ≥ 1.5V (min) with 54Ω load
• Output Current Limit: 60 mA (max)
• Propagation Delay: 20 ns (typical)

Receiver Section

• Input Sensitivity: ±200 mV
• Input Resistance: 12 kΩ (min)
• Input Hysteresis: 50 mV (typical)
• Common-Mode Input Range: -7V to +12V
• Output Rise/Fall Time: 10 ns (typical)

Thermal Characteristics

• Thermal Shutdown Threshold: ~150°C junction temperature
• Thermal Resistance (Junction-to-Air): 80°C/W (typical)

Functional Description

Driver Truth Table

• Input D = H → Output Y = H, Output Z = L
• Input D = L → Output Y = L, Output Z = H

Receiver Truth Table

• VID ≥ +0.2V → Output R = H
• -0.2V < VID < +0.2V → Output R = indeterminate
• VID ≤ -0.2V → Output R = L
• Inputs open → Output R = H

Package Information

The SN75179B is available in the following package options:

• 16-pin PDIP (Plastic Dual In-line Package)
  • Package code: N
  • Dimensions: 19.30mm x 6.35mm
  • Lead pitch: 2.54mm
• 16-pin SOIC (Small Outline Integrated Circuit)
  • Package code: D
  • Dimensions: 9.90mm x 3.91mm
  • Lead pitch: 1.27mm

Design Considerations

When implementing the SN75179B in system designs, consider the following:

• Termination resistors should match the characteristic impedance of the transmission line
• Proper decoupling capacitors (0.1μF) should be placed near the power supply pins
• For long cable runs, consider using twisted pair cables with proper shielding
• The thermal shutdown feature provides protection but should not be relied upon for normal operation
• Ensure common-mode voltage limits are not exceeded in the application

Reliability and Compliance

The SN75179B meets or exceeds the following reliability standards:

• ESD Protection: ≥ 2000V (Human Body Model)
• Manufactured under Texas Instruments' quality management system
• RoHS compliant (when ordered with appropriate suffix)

Ordering Information

The device is available in several package and temperature options:

• SN75179BN - PDIP package, commercial temperature range
• SN75179BD - SOIC package, commercial temperature range