SNVSA47D February   2016  – December 2022 LM5165

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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 Switching Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Integrated Power MOSFETs
      2. 7.3.2  Selectable PFM or COT Mode Converter Operation
      3. 7.3.3  COT Mode Light-Load Operation
      4. 7.3.4  Low Dropout Operation and 100% Duty Cycle Mode
      5. 7.3.5  Adjustable Output Voltage (FB)
      6. 7.3.6  Adjustable Current Limit
      7. 7.3.7  Precision Enable (EN) and Hysteresis (HYS)
      8. 7.3.8  Power Good (PGOOD)
      9. 7.3.9  Configurable Soft Start (SS)
      10. 7.3.10 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Standby Mode
      3. 7.4.3 Active Mode in COT
      4. 7.4.4 Active Mode in PFM
      5. 7.4.5 Sleep Mode in PFM
  8. 8 Applications and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Design 1: Wide VIN, Low IQ COT Converter Rated at 5 V, 150 mA
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Custom Design With WEBENCH® Tools
          2. 8.2.1.2.2 Switching Frequency – RT
          3. 8.2.1.2.3 Filter Inductor – LF
          4. 8.2.1.2.4 Output Capacitors – COUT
          5. 8.2.1.2.5 Series Ripple Resistor – RESR
          6. 8.2.1.2.6 Input Capacitor – CIN
          7. 8.2.1.2.7 Soft-Start Capacitor – CSS
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Design 2: Small Solution Size PFM Converter Rated at 3.3 V, 50 mA
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Peak Current Limit Setting – RILIM
          2. 8.2.2.2.2 Switching Frequency – LF
          3. 8.2.2.2.3 Output Capacitor – COUT
          4. 8.2.2.2.4 Input Capacitor – CIN
        3. 8.2.2.3 Application Curves
      3. 8.2.3 Design 3: High Density 12-V, 75-mA PFM Converter
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
          1. 8.2.3.2.1 Peak Current Limit Setting – RILIM
          2. 8.2.3.2.2 Switching Frequency – LF
          3. 8.2.3.2.3 Input and Output Capacitors – CIN, COUT
          4. 8.2.3.2.4 Feedback Resistors – RFB1, RFB2
          5. 8.2.3.2.5 Undervoltage Lockout Setpoint – RUV1, RUV2, RHYS
          6. 8.2.3.2.6 Soft Start – CSS
        3. 8.2.3.3 Application Curves
      4. 8.2.4 Design 4: 3.3-V, 150-mA COT Converter With High Efficiency
        1. 8.2.4.1 Design Requirements
        2. 8.2.4.2 Application Curves
      5. 8.2.5 Design 5: 15-V, 150-mA, 600-kHz COT Converter
        1. 8.2.5.1 Design Requirements
        2. 8.2.5.2 Detailed Design Procedure
          1. 8.2.5.2.1 COT Output Ripple Voltage Reduction
        3. 8.2.5.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
        1. 8.4.1.1 Compact PCB Layout for EMI Reduction
        2. 8.4.1.2 Feedback Resistor Layout
      2. 8.4.2 Layout Example
  9. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
      2. 9.1.2 Development Support
      3. 9.1.3 Custom Design With WEBENCH® Tools
    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
  10. 10Mechanical, Packaging, and Orderable Information

8.4.1.1 Compact PCB Layout for EMI Reduction

Radiated EMI generated by high di/dt components relates to pulsing currents in switching converters. The larger area covered by the path of a pulsing current, the more electromagnetic emission is generated. The key to minimize radiated EMI is to identify the pulsing current path and minimize the area of that path.

The critical switching loop of the power stage in terms of EMI is denoted in Figure 8-36. The topological architecture of a buck converter means that a particularly high di/dt current effective path exists in the loop comprising the input capacitor and the LM5165 integrated MOSFETs, and it becomes mandatory to reduce the parasitic inductance of this loop by minimizing the effective loop area.

GUID-1E055354-780C-4863-8BC1-598FE9A89B6D-low.gifFigure 8-36 Synchronous Buck Converter With Power Stage Critical Switching Loop

The input capacitor provides the primary path for the high di/dt components of the high-side MOSFET current. Placing a ceramic capacitor as close as possible to the VIN and GND pins is the key to EMI reduction. Keep the trace connecting SW to the inductor as short as possible and just wide enough to carry the load current without excessive heating. Use short, thick traces or copper pours (shapes) for current conduction path to minimize parasitic resistance. Place the output capacitor close to the VOUT side of the inductor, and connect the capacitor return terminal to the LM5165 GND pin and exposed PAD.