SNOSB24C October   2008  – November 2025 LM5576-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Shutdown / Standby
      2. 6.3.2 Soft Start
      3. 6.3.3 Thermal Protection
    4. 6.4 Device Functional Modes
      1. 6.4.1 High Voltage Start-Up Regulator
      2. 6.4.2 Oscillator and Sync Capability
      3. 6.4.3 Error Amplifier and PWM Comparator
      4. 6.4.4 Ramp Generator
      5. 6.4.5 Maximum Duty Cycle / Input Dropout Voltage
      6. 6.4.6 Boost Pin
      7. 6.4.7 Current Limit
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Bias Power Dissipation Reduction
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1  Custom Design With WEBENCH® Tools
        2. 7.2.2.2  External Components
        3. 7.2.2.3  R3 (RT)
        4. 7.2.2.4  L1
        5. 7.2.2.5  C3 (CRAMP)
        6. 7.2.2.6  C9, C10
        7. 7.2.2.7  D1
        8. 7.2.2.8  C1, C2
        9. 7.2.2.9  C8
        10. 7.2.2.10 C7
        11. 7.2.2.11 C4
        12. 7.2.2.12 R5, R6
        13. 7.2.2.13 R1, R2, C12
        14. 7.2.2.14 R7, C11
        15. 7.2.2.15 R4, C5, C6
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
      3. 7.4.3 Power Dissipation
      4. 7.4.4 Thermal Considerations
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Development Support
        1. 8.1.1.1 Custom Design With WEBENCH® Tools
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.2.2.3 R3 (RT)

RT sets the oscillator switching frequency. Generally, higher frequency applications are smaller but have higher losses. Operation at 300kHz was selected for this example as a reasonable compromise for both small size and high efficiency. The value of RT for 300kHz switching frequency can be calculated by Equation 9:

Equation 9. LM5576-Q1

The nearest standard value of 21kΩ was chosen for RT.