SNVSBS7A December   2021  – September 2022 LM5168 , LM5169

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  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  Control Architecture
      2. 8.3.2  Internal VCC Regulator and Bootstrap Capacitor
      3. 8.3.3  Internal Soft Start
      4. 8.3.4  On-Time Generator
      5. 8.3.5  Current Limit
      6. 8.3.6  N-Channel Buck Switch and Driver
      7. 8.3.7  Synchronous Rectifier
      8. 8.3.8  Enable, Undervoltage Lockout (EN/UVLO)
      9. 8.3.9  Power Good (PGOOD)
      10. 8.3.10 Thermal Protection
    4. 8.4 Device Functional Modes
      1. 8.4.1 Shutdown Mode
      2. 8.4.2 Active Mode
      3. 8.4.3 Sleep Mode
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Fly-Buck™ Converter Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1  Switching Frequency (RT)
        2. 9.2.2.2  Transformer Selection
        3. 9.2.2.3  Output Capacitor Selection
        4. 9.2.2.4  Secondary Output Diode
        5. 9.2.2.5  Setting Output Voltage
        6. 9.2.2.6  Input Capacitor
        7. 9.2.2.7  Type-3 Ripple Network
        8. 9.2.2.8  CBST Selection
        9. 9.2.2.9  Minimum Secondary Output Load
        10. 9.2.2.10 Example Design Summary
      3. 9.2.3 Application Curves
    3. 9.3 Typical Buck Application
      1. 9.3.1 Design Requirements
      2. 9.3.2 Detailed Design Procedure
        1. 9.3.2.1 Switching Frequency (RT)
        2. 9.3.2.2 Buck Inductor Selection
        3. 9.3.2.3 Setting the Output Voltage
        4. 9.3.2.4 Type-3 Ripple Network
        5. 9.3.2.5 Output Capacitor Selection
        6. 9.3.2.6 Input Capacitor Considerations
        7. 9.3.2.7 CBST Selection
        8. 9.3.2.8 Example Design Summary
      3. 9.3.3 Application Curves
    4. 9.4 Power Supply Recommendations
    5. 9.5 Layout
      1. 9.5.1 Thermal Considerations
      2. 9.5.2 Typical EMI Results
      3. 9.5.3 Layout Guidelines
        1. 9.5.3.1 Compact PCB Layout for EMI Reduction
        2. 9.5.3.2 Feedback Resistors
      4. 9.5.4 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Third-Party Products Disclaimer
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Support Resources
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.3.7 Synchronous Rectifier

The LM516x provides an internal low-side synchronous rectifier N-channel MOSFET. This MOSFET provides a low-resistance path for the inductor current to flow when the high-side MOSFET is turned off.

The synchronous rectifier operates in a diode emulation mode. Diode emulation enables the regulator to operate in a pulse-skipping mode during light load conditions. This mode leads to a reduction in the average switching frequency at light loads. Switching losses and FET gate driver losses, both of which are proportional to switching frequency, are significantly reduced at very light loads and efficiency is improved. This pulse-skipping mode also reduces the circulating inductor current and losses associated with conventional CCM at light loads.