ZHCS529I January   2007  – April 2025 LM25574

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
    4. 6.4 Device Functional Modes
      1. 6.4.1 Shutdown and Standby Mode
      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 and Input Drop-out Voltage
      6. 6.4.6 Current Limit
      7. 6.4.7 Soft-Start
      8. 6.4.8 Boost Pin
      9. 6.4.9 Thermal Protection
  8. 7 Application and Implementation
    1. 7.1 Application Information
    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  External Components
        3. 7.2.3.3  R3 -RT Resistor
        4. 7.2.3.4  L1-Inductor
        5. 7.2.3.5  C3 (CRAMP)
        6. 7.2.3.6  C9-Output Capacitor
        7. 7.2.3.7  C1-Input Capacitor
        8. 7.2.3.8  C8- VCC Capacitor
        9. 7.2.3.9  C7- BST capacitor
        10. 7.2.3.10 C4 - SS Capacitor
        11. 7.2.3.11 R5, R6 - Feedback Resistor
        12. 7.2.3.12 R1, R2, C2 - SD Pin Components
        13. 7.2.3.13 R4, C5, C6 - Compensation Components
        14. 7.2.3.14 Bias Power Dissipation Reduction
      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 接收文档更新通知
    3. 8.3 支持资源
    4. 8.4 Trademarks
    5. 8.5 静电放电警告
    6. 8.6 术语表
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

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机械数据 (封装 | 引脚)
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订购信息

7.2.3.4 L1-Inductor

The inductor value is determined based on the operating frequency, load current, ripple current, and the minimum and maximum input voltage (VIN(min), VIN(max)).

LM25574 Inductor Current WaveformFigure 7-2 Inductor Current Waveform

To keep the circuit in continuous conduction mode (CCM), the maximum ripple current IRIPPLE must be less than twice the minimum load current, or 0.2 Ap-p. Using this value of ripple current, the value of inductor (L1) is calculated using the following:

Equation 6. LM25574
Equation 7. LM25574

This procedure provides a guide to select the value of L1. The nearest standard value (100µH) is used. L1 must be rated for the peak current (IPK+) to prevent saturation. During normal loading conditions, the peak current occurs at maximum load current plus maximum ripple. During an overload condition the peak current is limited to 0.7A nominal (0.85A maximum). The selected inductor (see Equation 7) has a conservative 1.0 Amp saturation current rating. For this manufacturer, the saturation rating is defined as the current necessary for the inductance to reduce by 30%, at 20°C.