SLLS261N July   1997  – April 2021 SN55LVDS31 , SN65LVDS31 , SN65LVDS3487 , SN65LVDS9638

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (Continued)
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings (1)
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics: SN55LVDS31
    6. 7.6 Electrical Characteristics: SN65LVDSxxxx
    7. 7.7 Switching Characteristics: SN55LVDS31
    8. 7.8 Switching Characteristics: SN65LVDSxxxx
    9. 7.9 Typical Characteristics
      1. 7.9.1 17
  8. 8 Parameter Measurement Information
    1. 8.1 19
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Driver Disabled Output
      2. 9.3.2 NC Pins
      3. 9.3.3 Unused Enable Pins
      4. 9.3.4 Driver Equivalent Schematics
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Point-to-Point Communications
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
          1. 10.2.1.2.1 Driver Supply Voltage
          2. 10.2.1.2.2 Driver Bypass Capacitance
          3. 10.2.1.2.3 Driver Output Voltage
          4. 10.2.1.2.4 Interconnecting Media
          5. 10.2.1.2.5 PCB Transmission Lines
          6. 10.2.1.2.6 Termination Resistor
          7. 10.2.1.2.7 Driver NC Pins
        3. 10.2.1.3 Application Curve
      2. 10.2.2 Multidrop Communications
        1. 10.2.2.1 Design Requirements
        2. 10.2.2.2 Detailed Design Procedure
          1. 10.2.2.2.1 Interconnecting Media
        3. 10.2.2.3 Application Curve
  11. 11Power Supply Recommendations
    1. 11.1 49
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 Microstrip vs. Stripline Topologies
      2. 12.1.2 Dielectric Type and Board Construction
      3. 12.1.3 Recommended Stack Layout
      4. 12.1.4 Separation Between Traces
      5. 12.1.5 Crosstalk and Ground Bounce Minimization
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Other LVDS Products
    2. 13.2 Documentation Support
      1. 13.2.1 Related Information
      2. 13.2.2 Receiving Notification of Documentation Updates
      3. 13.2.3 Related Links
    3. 13.3 Support Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

12.1.4 Separation Between Traces

The separation between traces depends on several factors; however, the amount of coupling that can be tolerated usually dictates the actual separation. Low-noise coupling requires close coupling between the differential pair of an LVDS link to benefit from the electromagnetic field cancellation. The traces should be 100-Ω differential and thus coupled in the manner that best fits this requirement. In addition, differential pairs should have the same electrical length to ensure that they are balanced, thus minimizing problems with skew and signal reflection.

In the case of two adjacent single-ended traces, one should use the 3-W rule, which stipulates that the distance between two traces should be greater than two times the width of a single trace, or three times its width measured from trace center to trace center. This increased separation effectively reduces the potential for crosstalk. The same rule should be applied to the separation between adjacent LVDS differential pairs, whether the traces are edge-coupled or broad-side-coupled.

GUID-E1FBB273-1F93-4AB9-B7AC-4D4F08128E61-low.gifFigure 12-5 3-W Rule for Single-Ended and Differential Traces (Top View)

You should exercise caution when using autorouters, because they do not always account for all factors affecting crosstalk and signal reflection. For instance, it is best to avoid sharp 90° turns to prevent discontinuities in the signal path. Using successive 45° turns tends to minimize reflections.