SLOS451C December   2004  – March 2025 THS4631

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Related Products
  6. 5 Pin Configuration Functions
  7. 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 Electrical Characteristics
    6. 6.6 Typical Characteristics
  8. 7 Parameter Measurement Information
  9. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Transimpedance Fundamentals
      2. 8.1.2 Noise Analysis
    2. 8.2 Typical Applications
      1. 8.2.1 Wideband Photodiode Transimpedance Amplifier
        1. 8.2.1.1 Detailed Design Procedure
          1. 8.2.1.1.1 Designing the Transimpedance Circuit
          2. 8.2.1.1.2 Measuring Transimpedance Bandwidth
          3. 8.2.1.1.3 Summary of Key Decisions in Transimpedance Design
          4. 8.2.1.1.4 Selection of Feedback Resistors
        2. 8.2.1.2 Application Curves
      2. 8.2.2 Alternative Transimpedance Configurations
    3. 8.3 Power Supply Recommendations
      1. 8.3.1 Slew-Rate Performance With Varying Input-Step Amplitude and Rise-and-Fall Time
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
        1. 8.4.1.1 Printed-Circuit Board (PCB) Layout Techniques for High Performance
        2. 8.4.1.2 PowerPAD Design Considerations
        3. 8.4.1.3 PowerPAD PCB Layout Considerations
        4. 8.4.1.4 Power Dissipation and Thermal Considerations
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Design Tools Evaluation Fixture, Spice Models, and Applications Support
        1. 9.1.1.1 Bill of Materials
        2. 9.1.1.2 EVM
        3. 9.1.1.3 EVM Warnings and Restrictions
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

8.4.1.3 PowerPAD PCB Layout Considerations

  1. Figure 8-14 and Figure 8-15 show the PCB with a top-side etch pattern. There must be etch for the leads and for the thermal pad.
  2. Place the recommended number of vias in the area of the thermal pad. These vias must be 10 mils in diameter. Keep the vias small so that solder wicking through the vias is not a problem during reflow.
  3. Place additional vias anywhere along the thermal plane outside of the thermal pad area. Additional vias help dissipate the heat generated by the THS4631. These additional vias can be larger than the 10-mil diameter vias directly under the thermal pad because the vias are not in the thermal pad area to be soldered; therefore, wicking is not a problem.
  4. Connect all thermal pad vias to the internal ground plane. Although the PowerPAD is electrically isolated from all pins and the active circuitry, connection to the ground plane is recommended to improve thermal performance. Ground planes are typically the largest copper area on the PCB and help to move heat across the PCB. After the heat spreads across the PCB, airflow can move across a larger surface area to remove heat from the system.
  5. When connecting these vias to the ground plane, do not use the typical web or spoke via connection methodology. Web connections have a high thermal resistance connection that is useful for slowing heat transfer, which makes the soldering of vias that have plane connections easier. In this application, however, low thermal resistance is desired for the most efficient heat transfer. Therefore, the vias under the THS4631 PowerPAD package must make a connection to the internal ground plane with a complete connection around the entire circumference of the via.
  6. For the top-side solder mask, leave the terminals of the package and the thermal pad area with via holes exposed. The bottom-side solder mask must cover the via holes of the thermal pad area. This configuration prevents solder from being pulled away from the thermal pad area during the reflow process.
  7. Apply solder paste to the exposed thermal pad area and all of the device terminals.
  8. With these preparatory steps in place, the device is simply placed in position and run through the solder reflow operation as any standard surface-mount component.

Following these steps results in a device that is properly installed.