SNVSB28A December   2017  – April 2026 LM25575-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 High Voltage Start-Up Regulator
    4. 6.4 Device Functional Modes
      1. 6.4.1 Shutdown and Stand-by Mode
      2. 6.4.2 Error Amplifier and PWM Comparator
      3. 6.4.3 Ramp Generator
      4. 6.4.4 Maximum Duty Cycle and Input Drop-out Voltage
      5. 6.4.5 Current Limit
      6. 6.4.6 Soft Start
      7. 6.4.7 Boost Pin
      8. 6.4.8 Thermal Protection
  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 Typical Schematic for High Frequency (1MHz) Application
      2. 7.2.2 Design Requirements
      3. 7.2.3 Detailed Design Procedure
        1. 7.2.3.1  Custom Design With WEBENCH® Tools
        2. 7.2.3.2  R3 (RT)
        3. 7.2.3.3  L1
        4. 7.2.3.4  C3 (CRAMP)
        5. 7.2.3.5  C9, C10
        6. 7.2.3.6  D1
        7. 7.2.3.7  C1, C2
        8. 7.2.3.8  C8
        9. 7.2.3.9  C7
        10. 7.2.3.10 C4
        11. 7.2.3.11 R5, R6
        12. 7.2.3.12 R1, R2, C12
        13. 7.2.3.13 R7, C11
        14. 7.2.3.14 R4, C5, C6
      4. 7.2.4 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
        1. 7.4.1.1 PCB Layout and Thermal Considerations
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Developmental 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

7.2.3.12 R1, R2, C12

A voltage divider can be connected to the SD pin to set a minimum operating voltage VIN(min) for the regulator. If this feature is required, the easiest approach to select the divider resistor values is to select a value for R1 (between 10kΩ and 100kΩ recommended) then calculate R2 from Equation 11:

Equation 11. LM25575-Q1

Capacitor C12 provides filtering for the divider. The voltage at the SD pin must never exceed 8V, when using an external set-point divider it can be necessary to clamp the SD pin at high input voltage conditions. The reference design utilizes the full range of the LM25575-Q1 (6V to 42V); therefore these components can be omitted. With the SD pin open circuit the LM25575-Q1 responds once the VCC UVLO threshold is satisfied.