SLLSF21D September   2018  – February  2020

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Simplified Schematic
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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: Driver
    10. 6.10 Electrical Characteristics: Receiver
    11. 6.11 Supply Current Characteristics: Side 1(ICC1)
    12. 6.12 Supply Current Characteristics: Side 2(ICC2)
    13. 6.13 Switching Characteristics: Driver
    14. 6.14 Switching Characteristics: Receiver
    15. 6.15 Insulation Characteristics Curves
    16. 6.16 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Electromagnetic Compatibility (EMC) Considerations
      2. 8.3.2 Failsafe Receiver
      3. 8.3.3 Thermal Shutdown
      4. 8.3.4 Glitch-Free Power Up and Power Down
    4. 8.4 Device Functional Modes
      1. 8.4.1 Device I/O Schematics
  9. 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 and Bus Length
        2. 9.2.2.2 Stub Length
        3. 9.2.2.3 Bus Loading
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 PCB Material
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resource
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

9.2.2.3 Bus Loading

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 12 kΩ. Standard-compliant drivers must be able to drive 32 of these ULs.

The ISO1500 device has 1/8 UL impedance transceiver and can connect up to 256 nodes to the bus.