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

PRODUCTION DATA  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Description (Continued)
  6. Pin Configuration and Functions
  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. Parameter Measurement Information
    1. 8.1 19
  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

Layout Example

At least two or three times the width of an individual trace should separate single-ended traces and differential pairs to minimize the potential for crosstalk. Single-ended traces that run in parallel for less than the wavelength of the rise or fall times usually have negligible crosstalk. Increase the spacing between signal paths for long parallel runs to reduce crosstalk. Boards with limited real estate can benefit from the staggered trace layout, as shown in Figure 12-6.

GUID-38789EA7-4302-4DFA-9771-C4865B963F02-low.gifFigure 12-6 Staggered Trace Layout

This configuration lays out alternating signal traces on different layers; thus, the horizontal separation between traces can be less than 2 or 3 times the width of individual traces. To ensure continuity in the ground signal path, TI recommends having an adjacent ground via for every signal via, as shown in Figure 12-7. Note that vias create additional capacitance. For example, a typical via has a lumped capacitance effect of 0.5 pF to 1 pF in FR4.

GUID-6F9005AC-7266-4E48-9293-A63654D8E483-low.gifFigure 12-7 Ground Via Location (Side View)

Short and low-impedance connection of the device ground pins to the PCB ground plane reduces ground bounce. Holes and cutouts in the ground planes can adversely affect current return paths if they create discontinuities that increase returning current loop areas.

To minimize EMI problems, TI recommends avoiding discontinuities below a trace (for example, holes, slits, and so on) and keeping traces as short as possible. Zoning the board wisely by placing all similar functions in the same area, as opposed to mixing them together, helps reduce susceptibility issues.