SLLS552G December   2002  – September 2022 SN65HVD20 , SN65HVD21 , SN65HVD22 , SN65HVD23 , SN65HVD24

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Device Comparison
  7. 7 Pin Configuration and Functions
  8. 8 Specifications
    1. 8.1  Absolute Maximum Ratings
    2. 8.2  ESD Ratings
    3. 8.3  Recommended Operating Conditions
    4. 8.4  Thermal Information
    5. 8.5  Driver Electrical Characteristics
    6. 8.6  Receiver Electrical Characteristics
    7. 8.7  Driver Switching Characteristics
    8. 8.8  Receiver Switching Characteristics
    9. 8.9  Receiver Equalization Characteristics
    10. 8.10 Power Dissipation
    11. 8.11 Typical Characteristics
  9. 9 Parameter Measurement Information
  10. 10Detailed Description
    1. 10.1 Overview
    2. 10.2 Functional Block Diagram
    3. 10.3 Feature Description
    4. 10.4 Device Functional Modes
      1. 10.4.1 Test Mode Driver Disable
      2. 10.4.2 Equivalent Input and Output Schematic Diagrams
  11. 11Application and Implementation
    1. 11.1 Application Information
    2. 11.2 Typical Application
      1. 11.2.1 Design Requirements
      2. 11.2.2 Detailed Design Procedure
        1. 11.2.2.1 Noise Considerations for Equalized Receivers
      3. 11.2.3 Application Curves
  12. 12Power Supply Recommendations
  13. 13Layout
    1. 13.1 Layout Guidelines
    2. 13.2 Layout Example
  14. 14Device and Documentation Support
    1. 14.1 Receiving Notification of Documentation Updates
    2. 14.2 Support Resources
    3. 14.3 Trademarks
    4. 14.4 Electrostatic Discharge Caution
    5. 14.5 Glossary
  15. 15Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

11.2.1 Design Requirements

As the distances between nodes in an RS-485 network become greater and greater, it becomes more of a challenge to ensure reliable communication. The increased distance often means that the reference (ground) potentials has more of a difference between nodes. These ground potential differences give rise to differences in the common-mode voltages seen by the various transceivers on the bus. Standard RS-485 transceivers are typically specified to operate over a common-mode voltage from –7 V to 12 V, which may be insufficient for larger distances. The SN65HVD2x family of devices extends this range to –20 V to 25 V, allowing for greater communication distances between nodes.

Increased cable lengths can lead to increased jitter, especially in links operating at high data rates. This increased jitter is due to the attenuation of the cable, which tends to increase with frequency. Having unequal loss between higher and lower frequencies causes the RS-485 signal to distort, adding some timing deviation (jitter) to the edge crossings of the RS-485 data. If the jitter amplitude exceeds the jitter tolerance of the receiving MCU or UART, then bit errors are likely to result in the link. However, jitter can be reduced for a given link through the use of receiver equalization.