SLVS441D December   2002  – December  2014 TPS61042

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Typical Application
  5. 5 Revision History
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Boost Converter
      2. 8.3.2 Peak Current Control (Boost Converter)
      3. 8.3.3 Softstart
      4. 8.3.4 Control (CTRL)
      5. 8.3.5 Applying a PWM Signal to the CTRL Pin with an On-Time tp≤2.5µs
    4. 8.4 Device Functional Modes
      1. 8.4.1 Overvoltage Protection (OVP)
      2. 8.4.2 Undervoltage Lockout
      3. 8.4.3 Thermal Shutdown
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Efficiency
      2. 9.1.2 Setting The LED Current
      3. 9.1.3 PWM Control With Separate Enable
      4. 9.1.4 Example Schematics
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Inductor Selection, Maximum Load Current, and Switching Frequency
        2. 9.2.2.2 Output Capacitor Selection and Line Regulation
        3. 9.2.2.3 Input Capacitor Selection
        4. 9.2.2.4 Diode Selection
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
      1. 11.2.1 Thermal Considerations
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

11 Layout

11.1 Layout Guidelines

In all switching power supplies the layout is an important step in the design, especially at high peak currents and switching frequencies. If the layout is not carefully done, the regulator might show noise problems and duty cycle jitter.

The input capacitor should be placed as close as possible to the input pin for good input voltage filtering. The inductor and diode must be placed as close as possible to the switch pin to minimize noise coupling into other circuits. Since the feedback pin and network is a high impedance circuit, the feedback network should be routed away from the inductor.

11.2 Layout Example

TPS61042_layout.gifFigure 27. Layout Example

11.2.1 Thermal Considerations

The TPS61042 comes in a thermally enhanced QFN package. The package includes a thermal pad improving the thermal capabilities of the package. See the QFN/SON PCB Attachment application note (SLUA271).

The thermal resistance junction to ambient RΘJA of the QFN package greatly depends on the PCB layout. Using thermal vias and wide PCB traces improves the thermal resistance RΘJA. Under normal operation conditions no PCB vias are required for the thermal pad. However, the thermal PowerPAD™ must be soldered to the PCB.