SLOS451D December   2004  – March 2026 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

8.4.1.4 Power Dissipation and Thermal Considerations

To maintain maximum output capabilities, the THS4631 does not incorporate automatic thermal shutoff protection. The designer must take care that the design does not violate the absolute maximum junction temperature of the device. Failure can result if the absolute maximum junction temperature of 150°C is exceeded. For best performance, design for a maximum junction temperature of 125°C. Between 125°C and 150°C, damage does not occur, but the performance of the amplifier begins to degrade. The thermal characteristics of the device are dictated by the package and the PCB. Maximum power dissipation for a given package is calculated using Equation 9.

Equation 9. THS4631

where:

  • PDmax is the maximum power dissipation in the amplifier (W).
  • Tmax is the absolute maximum junction temperature (°C).
  • TA is the ambient temperature (°C).
  • θJA = θJC + θCA
  • θJC is the thermal coefficient from the silicon junctions to the case (°C/W).
  • θCA is the thermal coefficient from the case to ambient air (°C/W).
Note: For systems where heat dissipation is more critical, the THS4631 is offered in an 8-pin HVSSOP with PowerPAD package and an 8-pin HSOIC with PowerPAD package with better thermal performance. The thermal coefficient for the PowerPAD packages are substantially improved over the traditional SOIC. Maximum power dissipation levels are depicted in Figure 8-13 for the available packages. The data for the PowerPAD packages assume a board layout that follows the PowerPAD layout guidelines referenced previously, and detailed in the PowerPAD™ Thermally Enhanced Package application note. Figure 8-13 also illustrates the effect of not soldering the PowerPAD to a PCB. The thermal impedance increases substantially, which can cause serious heat and performance issues. Always solder the PowerPAD to the PCB for optimized performance.
THS4631 Maximum Power Dissipation vs Ambient Temperature Figure 8-13 Maximum Power Dissipation vs Ambient Temperature

Results are with no air flow and PCB size = 3" × 3".

  • θJA = 58.4°C/W for the 8-pin HVSSOP with PowerPAD (DGN).
  • θJA = 98°C/W for the 8-pin SOIC high-K test PCB (D).
  • θJA = 158°C/W for the 8-pin HVSSOP with PowerPAD, without solder.

When determining whether or not the device satisfies the maximum power dissipation requirement, consider not only quiescent power dissipation, but also dynamic power dissipation. Often, this dynamic dissipation is difficult to quantify because the signal pattern is inconsistent, but an estimate of the RMS power dissipation can provide visibility into a possible problem.