SLLSF86D May   2018  – August 2026 ISOW1412 , ISOW1432

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 6 Specifications
    1. 6.1  Absolute Maximum Ratings
    2. 6.2  ESD Ratings
    3. 6.3  Recommended Operating Conditions
    4. 6.4  Thermal Information
    5. 6.5  Power Ratings
    6. 6.6  Insulation Specifications
    7. 6.7  Safety-Related Certifications
    8. 6.8  Safety Limiting Values
    9. 6.9  Electrical Characteristics
    10. 6.10 Supply Current Characteristics at VISOOUT = 3.3 V
    11. 6.11 Supply Current Characteristics at  VISOOUT = 5 V
    12. 6.12 Switching Characteristics at VISOOUT = 3.3 V
    13. 6.13 Switching Characteristics at VISOOUT = 5 V
    14. 6.14 Insulation Characteristics Curves
    15. 6.15 Typical Characteristics
  8. 7 Parameter Measurement Information
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Power Isolation
    3. 8.3 Signal Isolation
    4. 8.4 RS-485
    5. 8.5 Functional Block Diagram
    6. 8.6 Feature Description
      1. 8.6.1 Power-Up and Power-Down Behavior
      2. 8.6.2 Protection Features
      3. 8.6.3 Failsafe Receiver
      4. 8.6.4 Glitch-Free Power Up and Power Down
    7. 8.7 Device Functional Modes
    8. 8.8 Device I/O Schematics
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Data Rate, Bus Length and Bus Loading
        2. 9.2.2.2 Stub Length
      3. 9.2.3 Insulation Lifetime
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

9.2.2.1 Data Rate, Bus Length and Bus Loading

The RS-485 standard has typical curves similar to those shown in Figure 11-4. These curves show the inverse relationship between signaling rate and cable length. If the data rate of the payload between two nodes is lower, the cable length between the nodes can be longer. Use below Figure as a guideline for cable selection, data rate, cable length and subsequent jitter budgeting.

ISOW1412 ISOW1432 Cable Length vs Data Rate CharacteristicsFigure 9-4 Cable Length vs Data Rate Characteristics

The current supplied by the driver must supply into a load because the output of the driver depends on this current. Add transceivers to the bus to increase the total bus loading. The RS-485 standard specifies a hypothetical term of a unit load (UL) to estimate the maximum number of possible bus loads. The UL represents a load impedance of approximately 12kΩ. Standard-compliant drivers must be able to drive 32 of these ULs. The ISOW14x2 devices have 1/8 UL impedance transceiver and can connect up to 256 nodes to the bus.