ZHCSL47A April   2020  – January 2021 LM5181

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Integrated Power MOSFET
      2. 8.3.2  PSR Flyback Modes of Operation
      3. 8.3.3  Setting the Output Voltage
        1. 8.3.3.1 Diode Thermal Compensation
      4. 8.3.4  Control Loop Error Amplifier
      5. 8.3.5  Precision Enable
      6. 8.3.6  Configurable Soft Start
      7. 8.3.7  External Bias Supply
      8. 8.3.8  Minimum On-Time and Off-Time
      9. 8.3.9  Overcurrent Protection
      10. 8.3.10 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Standby Mode
      3. 8.4.3 Active Mode
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Design 1: Wide VIN, Low IQ PSR Flyback Converter Rated at 5 V, 0.5 A
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1  Custom Design With WEBENCH® Tools
          2. 9.2.1.2.2  Custom Design With Excel Quickstart Tool
          3. 9.2.1.2.3  Flyback Transformer – T1
          4. 9.2.1.2.4  Flyback Diode – DFLY
          5. 9.2.1.2.5  Zener Clamp Circuit – DF, DCLAMP
          6. 9.2.1.2.6  Output Capacitor – COUT
          7. 9.2.1.2.7  Input Capacitor – CIN
          8. 9.2.1.2.8  Feedback Resistor – RFB
          9. 9.2.1.2.9  Thermal Compensation Resistor – RTC
          10. 9.2.1.2.10 UVLO Resistors – RUV1, RUV2
          11. 9.2.1.2.11 Soft-Start Capacitor – CSS
      2. 9.2.2 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Examples
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 第三方产品免责声明
      2. 12.1.2 Development Support
        1. 12.1.2.1 Custom Design With WEBENCH® Tools
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 接收文档更新通知
    4. 12.4 支持资源
    5. 12.5 Trademarks
    6. 12.6 静电放电警告
    7. 12.7 术语表
  13. 13Mechanical, Packaging, and Orderable Information

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8.3.1 Integrated Power MOSFET

The LM5181 is a flyback dc/dc converter with integrated 100-V, 0.75-A N-channel power MOSFET. During the MOSFET on-time, the transformer primary current increases from zero with a slope of VIN / LMAG (where LMAG is the transformer primary-referred magnetizing inductance) while the output capacitor supplies the load current. When the MOSFET is turned off by the control logic, the SW voltage VSW swings up to approximately VIN + (NPS × VOUT), where NPS = NP / NS is the primary-to-secondary turns ratio of the transformer. The magnetizing current flows in the secondary side through the flyback diode, charging the output capacitor and supplying current to the load. Duty cycle D is defined as tON / tSW, where tON is the MOSFET conduction time and tSW is the switching period.

Figure 8-1 shows a typical schematic of the LM5181 PSR flyback circuit. Components denoted in red are optional depending on the application requirements.

GUID-F4A22124-62CF-4D83-A94A-D33469DC9EB6-low.gifFigure 8-1 LM5181 Flyback Converter Schematic (Optional Components in Red)