SLLSFM1 September   2022 SN6507-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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 Switching Characteristics
    7. 6.7 Typical Characteristics, SN6507-Q1
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Push-Pull Converter
      2. 8.3.2 Core Magnetization
      3. 8.3.3 Duty Cycle Control
      4.      Programmable Switching Frequency
      5. 8.3.4 Spread Spectrum Clocking
      6. 8.3.5 Slew Rate Control
      7. 8.3.6 Protection Features
        1. 8.3.6.1 Over Voltage Protection (OVP)
        2. 8.3.6.2 Over Current and Short Circuit Protection (OCP)
        3. 8.3.6.3 Under Voltage Lock-Out (UVLO)
        4. 8.3.6.4 Thermal Shut Down (TSD)
    4. 8.4 Device Functional Modes
      1. 8.4.1 Start-Up Mode
        1. 8.4.1.1 Soft-Start
      2. 8.4.2 Operation Mode
      3. 8.4.3 Shutdown Mode
      4. 8.4.4 SYNC Mode
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Pin Configuration
        2. 9.2.2.2 LDO Selection
        3. 9.2.2.3 Diode Selection
        4. 9.2.2.4 Capacitor and Inductor Selection
        5. 9.2.2.5 Transformer Selection
          1. 9.2.2.5.1 V-t Product Calculation
          2. 9.2.2.5.2 Turns Ratio Estimate
        6. 9.2.2.6 Low-Emissions Designs
      3. 9.2.3 Application Curves
      4. 9.2.4 System Examples
        1. 9.2.4.1 Higher Output Voltage Designs
        2. 9.2.4.2 Commercially-Available Transformers
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Community Resources
    4. 10.4 Trademarks
  11. 11Mechanical, Packaging, and Orderable Information

Package Options

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

9.2.2.3 Diode Selection

A rectifier diode should always possess low-forward voltage to provide as much voltage to the converter output as possible. However, when SN6507-Q1 is used in high-frequency switching applications, the diode must also possess a low total capacitance, a short recovery time and a current rating greater than the load current. Schottky diodes meet these requirements and are therefore strongly recommended in SN6507-Q1 push-pull converter designs.

The necessary diode reverse voltage rating, VR, is determined by the transformer secondary side voltage plus any voltage ringing. The voltage ringing, however, is difficult to predict, because it depends on multiple factors, such as loop resistance, the leakage inductance of the transformer, and the diode junction capacitance. As a rule of thumb, the diode voltage rating should be greater than 1.5 times the transformer turns ratio multiplied by the maximum input voltage. Because the two secondary windings are connected across the rectifier bridge, a factor of two is needed, producing the diode maximum DC blocking voltage rating:

Equation 7. Diode VR>1.5×2×N×VIN(MAX)
For high-efficiency designs, diodes with low forward voltage, VF, and diode capacitance, CT, can be used, like BAT165E6327HTSA1 or equivalent can be used for high-efficiency 15-V outputs. Diode parameters like these parasitics and reverse recovery will impact system efficiency and can affect emissions. For low-emissions designs, low-emissions diodes can be used, like PMEG200G20ELRX or equivalent can be used for low-emissions outputs up to 100 V.