SNVSB07C July   2018  – April 2019

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application
      2.      Typical Efficiency, VOUT = 5 V
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Integrated Power MOSFET
      2. 7.3.2  PSR Flyback Modes of Operation
      3. 7.3.3  Setting the Output Voltage
        1. 7.3.3.1 Diode Thermal Compensation
      4. 7.3.4  Control Loop Error Amplifier
      5. 7.3.5  Precision Enable
      6. 7.3.6  Configurable Soft Start
      7. 7.3.7  External Bias Supply
      8. 7.3.8  Minimum On-Time and Off-Time
      9. 7.3.9  Overcurrent Protection
      10. 7.3.10 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Standby Mode
      3. 7.4.3 Active Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Design 1: Wide VIN, Low IQ PSR Flyback Converter Rated at 5 V, 1 A
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1  Custom Design With WEBENCH® Tools
          2. 8.2.1.2.2  Custom Design With Excel Quickstart Tool
          3. 8.2.1.2.3  Flyback Transformer – T1
          4. 8.2.1.2.4  Flyback Diode – DFLY
          5. 8.2.1.2.5  Zener Clamp Circuit – DF, DCLAMP
          6. 8.2.1.2.6  Output Capacitor – COUT
          7. 8.2.1.2.7  Input Capacitor – CIN
          8. 8.2.1.2.8  Feedback Resistor – RFB
          9. 8.2.1.2.9  Thermal Compensation Resistor – RTC
          10. 8.2.1.2.10 UVLO Resistors – RUV1, RUV2
          11. 8.2.1.2.11 Soft-Start Capacitor – CSS
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Design 2: PSR Flyback Converter With Dual Outputs of 15 V and –7.7 V at 200 mA
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Flyback Transformer – T1
          2. 8.2.2.2.2 Flyback Diodes – DFLY1 and DFLY2
          3. 8.2.2.2.3 Input Capacitor – CIN
          4. 8.2.2.2.4 Feedback Resistor – RFB
          5. 8.2.2.2.5 UVLO Resistors – RUV1, RUV2
        3. 8.2.2.3 Application Curves
      3. 8.2.3 Design 3: PSR Flyback Converter With Stacked Dual Outputs of 24 V and 5 V
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
          1. 8.2.3.2.1 Flyback Transformer – T1
          2. 8.2.3.2.2 Feedback Resistor – RFB
          3. 8.2.3.2.3 UVLO Resistors – RUV1, RUV2
        3. 8.2.3.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
      2. 11.1.2 Development Support
      3. 11.1.3 Custom Design With WEBENCH® Tools
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.3.1 Integrated Power MOSFET

The LM5180-Q1 is a flyback dc/dc converter with integrated 100-V, 1.5-A N-channel power MOSFET. During the MOSFET on-time, the transformer primary current increases from zero with slope VIN / LMAG (where LMAG is the transformer primary-referred magnetizing inductance) while the output capacitor supplies the load current. When the high-side 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 19 shows a typical schematic of the LM5180-Q1 PSR flyback circuit. Components denoted in red are optional depending on the application requirements.

LM5180-Q1 Feature_desc_schematic_nvsb06.gifFigure 19. LM5180-Q1 Flyback Converter Schematic (Optional Components in Red)