SNVSCH2 September   2024 LM65645-Q1

ADVANCE INFORMATION  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and 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 System Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Descriptions
      1. 7.3.1 Output Voltage Selection
      2. 7.3.2 EN Pin and Use as VIN UVLO
      3. 7.3.3 Mode Selection
        1. 7.3.3.1 MODE/SYNC Pin Uses for Synchronization
        2. 7.3.3.2 Clock Locking
      4. 7.3.4 Adjustable Switching Frequency
      5. 7.3.5 Dual Random Spread Spectrum (DRSS)
      6. 7.3.6 Internal LDO, VCC UVLO, and BIAS Input
      7. 7.3.7 Bootstrap Voltage (BST Pin)
      8. 7.3.8 Soft Start and Recovery From Dropout
      9. 7.3.9 Safety Features
        1. 7.3.9.1 Power-Good Monitor
        2. 7.3.9.2 Overcurrent and Short-Circuit Protection
        3. 7.3.9.3 Hiccup
        4. 7.3.9.4 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Active Mode
        1. 7.4.2.1 Peak Current Mode Operation
        2. 7.4.2.2 Auto Mode Operation
          1. 7.4.2.2.1 Diode Emulation
        3. 7.4.2.3 FPWM Mode Operation
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Choosing the Switching Frequency
        3. 8.2.2.3 FB for Adjustable or Fixed Output Voltage Mode
        4. 8.2.2.4 Inductor Selection
        5. 8.2.2.5 Output Capacitor Selection
        6. 8.2.2.6 Input Capacitor Selection
        7. 8.2.2.7 CBOOT
        8. 8.2.2.8 External UVLO
        9. 8.2.2.9 Maximum Ambient Temperature
    3. 8.3 Best Design Practices
    4. 8.4 Power Supply Recommendations
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
        1. 8.5.1.1 Ground and Thermal Considerations
      2. 8.5.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 Third-Party Products Disclaimer
      2. 9.1.2 Development Support
        1. 9.1.2.1 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
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information
    1. 11.1 Tape and Reel Information

Package Options

Mechanical Data (Package|Pins)
  • RZT|20
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.2.2 Choosing the Switching Frequency

The choice of switching frequency is a compromise between conversion efficiency and overall design size. Lower switching frequency implies reduced switching losses and usually results in higher system efficiency. However, higher switching frequency allows the use of smaller inductors and output capacitors, hence, a more compact design. For this application example, we select a frequency of 2200kHz. In this case, the RT pin is connected to the GND. See Section 7.3.4 for more details.