SLVSAG3A September   2010  – December 2014 TPS61252

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Typical Application Schematic
  5. 5 Revision History
  6. 6 Device Options
  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 Electrical Characteristics
    6. 8.6 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
      1. 10.3.1  Operation
      2. 10.3.2  Current Limit Operation
      3. 10.3.3  Softstart
      4. 10.3.4  Enable
      5. 10.3.5  Under-Voltage Lockout (UVLO)
      6. 10.3.6  Power Good
      7. 10.3.7  Input Over Voltage Protection
      8. 10.3.8  Load Disconnect and Reverse Current Protection
      9. 10.3.9  Thermal Regulation
      10. 10.3.10 Thermal Shutdown
    4. 10.4 Device Functional Modes
      1. 10.4.1 Power Save Mode
      2. 10.4.2 100% Duty-Cycle Mode
  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 Output Voltage Setting
        2. 11.2.2.2 Input Current Limit
        3. 11.2.2.3 Maximum Output Current
        4. 11.2.2.4 Inductor Selection
        5. 11.2.2.5 Output Capacitor
        6. 11.2.2.6 Input Capacitor
        7. 11.2.2.7 Checking Loop Stability
      3. 11.2.3 Application Curves
  12. 12Power Supply Recommendations
  13. 13Layout
    1. 13.1 Layout Guidelines
    2. 13.2 Layout Example
    3. 13.3 Thermal Considerations
  14. 14Device and Documentation Support
    1. 14.1 Device Support
      1. 14.1.1 Third-Party Products Disclaimer
    2. 14.2 Trademarks
    3. 14.3 Electrostatic Discharge Caution
    4. 14.4 Glossary
  15. 15Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ

13 Layout

13.1 Layout Guidelines

For all switching power supplies, the layout is an important step in the design, especially at high peak currents and high switching frequencies. If the layout is not carefully done, the regulator could show stability problems as well as EMI problems. Therefore, use wide and short traces for the main current path and for the power ground tracks. The input capacitor, output capacitor, and the inductor should be placed as close as possible to the IC. Use a common ground node for power ground and a different one for control ground to minimize the effects of ground noise. Connect these ground nodes at any place close to one of the ground pins of the IC.

The feedback divider should be placed close to the IC to keep the feedback connection short. To lay out the ground, short and wide traces are recommended. This avoids ground shift problems, which can occur due to superimposition of power ground current onto the feedback divider. Figure 15 shows the recommended board layout.

13.2 Layout Example

TPS61252_Layout_Metric.gifFigure 15. Suggested Layout

13.3 Thermal Considerations

The implementation of integrated circuits in low-profile and fine-pitch surface-mount packages typically requires special attention to power dissipation. Many system-dependent issues such as thermal coupling, airflow, added heat sinks and convection surfaces, and the presence of other heat-generating components affect the power-dissipation limits of a given component.

Three basic approaches for enhancing thermal performance are listed below:

  • Improving the power dissipation capability of the PCB design
    • For example, increase of the GND plane on the top layer which is connected to the exposed thermal pad
    • Use thicker copper layer
  • Improving the thermal coupling of the component to the PCB
  • Introducing airflow in the system

Junction-to-ambient thermal resistance is highly application and board-layout dependent. In applications where high maximum power dissipation exists, special care must be paid to thermal dissipation issues in board design. The maximum junction temperature (TJ) of the TPS61252 is 150°C.