ZHCS527G January   2007  – April 2025 LM5574

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  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
      2. 6.3.2 Oscillator and Sync Capability
      3. 6.3.3 Error Amplifier and PWM Comparator
      4. 6.3.4 Ramp Generator
      5. 6.3.5 Maximum Duty Cycle, Input Dropout Voltage
      6. 6.3.6 Current Limit
      7. 6.3.7 Soft Start
      8. 6.3.8 Boost Pin
      9. 6.3.9 Thermal Protection
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
    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 (R)T
        4. 7.2.2.4  L1-Inductor
        5. 7.2.2.5  C3 (C)RAMP
        6. 7.2.2.6  C9-Output Capacitor
        7. 7.2.2.7  D1-Async Diode
        8. 7.2.2.8  C1-Input Capacitor
        9. 7.2.2.9  C8-VCC Capacitor
        10. 7.2.2.10 C7-BST Capacitor
        11. 7.2.2.11 C4- SS Capacitor
        12. 7.2.2.12 R5, R6- Feedback Resistors
        13. 7.2.2.13 R1, R2, C2-SD Pin Components
        14. 7.2.2.14 R4, C5, C6-Compensation Components
        15. 7.2.2.15 Bias Power Dissipation Reduction
      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 第三方产品免责声明
      2. 8.1.2 Development Support
        1. 8.1.2.1 Custom Design With WEBENCH® Tools
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 接收文档更新通知
    4. 8.4 支持资源
    5. 8.5 Trademarks
    6. 8.6 静电放电警告
    7. 8.7 术语表
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

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6.3.7 Soft Start

The soft-start feature allows the regulator to gradually reach the initial steady-state operating point, thus reducing start-up stresses and surges. The internal soft-start current source, set to 10µA, gradually increases the voltage of an external soft-start capacitor connected to the SS pin. The soft-start capacitor voltage is connected to the reference input of the error amplifier. Various sequencing and tracking schemes can be implemented using external circuits that limit or clamp the voltage level of the SS pin.

In the event a fault is detected (overtemperature, Vcc UVLO, SD) the soft-start capacitor is discharged. When the fault condition is no longer present a new soft-start sequence commences.