SLLSFT6 April   2026 THVD9491-SP

ADVANCE INFORMATION  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 ESD Ratings [IEC]
    4. 5.4 Recommended Operating Conditions
    5. 5.5 Thermal Information
    6. 5.6 Power Dissipation
    7. 5.7 Electrical Characteristics
    8. 5.8 Switching Characteristics: 20Mbps
    9. 5.9 Switching Characteristics: 50Mbps
  7. 6 Parameter Measurement Information
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1 Bus Fault Protection
      2. 7.3.2 Integrated IEC ESD and EFT Protection
      3. 7.3.3 Driver Overvoltage and Overcurrent Protection
      4. 7.3.4 Enhanced Receiver Noise Immunity
      5. 7.3.5 Receiver Fail-Safe Operation
      6. 7.3.6 Low-Power Shutdown Mode
    4. 7.4 Device Functional Modes
  9. 8 Application and Implementation
    1. 8.1 Typical Application
      1. 8.1.1 Design Requirements
      2. 8.1.2 Detailed Design Procedure
      3. 8.1.3 Application Curve
    2. 8.2 Power Supply Recommendations
    3. 8.3 Layout
      1. 8.3.1 Layout Guidelines
      2. 8.3.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information
    1.     PACKAGE OPTION ADDENDUM
    2. 11.1 Tape and Reel Information
    3. 11.2 Mechanical Data

8.1.2 Detailed Design Procedure

Figure 8-2 suggests a protection circuit against 1kV surge (IEC 61000-4-5) transients. Table 8-1 shows the associated bill of materials. SMAJ30CA TVS diodes are rated to operate up to 30V. This provides the protection diodes do not conduct if a direct RS-485 bus shorts to 24V DC industrial power rail.

THVD9491-SP Transient Protection Against Surge Transients for Full-Duplex DevicesFigure 8-2 Transient Protection Against Surge Transients for Full-Duplex Devices
Table 8-1 Components List
DEVICEFUNCTIONORDER NUMBERMANUFACTURER(1)
XCVRRS-485 transceiverTHVD9491-SPTI
TVSBidirectional 400W transient suppressorSMAJ30CALittelfuse
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