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

9.2.2.2 Stub Length

In an RS-485 network, the distance between the transceiver inputs and the cable trunk is known as the stub. The stub should be as short as possible when a node is connected to the bus. Stubs are a non-terminated piece of bus line that can introduce reflections of varying phase as the length of the stub increases. The electrical length, or round-trip delay, of a stub should be less than one-tenth of the rise time of the driver as a general guideline. Therefore, the maximum physical stub length (L(STUB)) is calculated as shown in Equation 3.

Equation 3. L(STUB) ≤ 0.1 × tr × v × c

where

  • tr is the 10/90 rise time of the driver.
  • c is the speed of light (3 × 108 m/s).
  • v is the signal velocity of the cable or trace as a factor of c.