SLLSEA0I February   2012  – January 2021 SN6501

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Revision History
  4. 4 Pin Configuration and Functions
  5. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 Handling Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Switching Characteristics
    7. 5.7 Typical Characteristics
  6. 6 Parameter Measurement Information
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Push-Pull Converter
      2. 7.3.2 Core Magnetization
    4. 7.4 Device Functional Modes
      1. 7.4.1 Start-Up Mode
      2. 7.4.2 Operating Mode
      3. 7.4.3 Off-Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 SN6501 Drive Capability
        2. 8.2.2.2 LDO Selection
        3. 8.2.2.3 Diode Selection
        4. 8.2.2.4 Capacitor Selection
        5. 8.2.2.5 Transformer Selection
          1. 8.2.2.5.1 V-t Product Calculation
          2. 8.2.2.5.2 Turns Ratio Estimate
          3. 8.2.2.5.3 Recommended Transformers
      3. 8.2.3 Application Curve
      4. 8.2.4 Higher Output Voltage Designs
      5. 8.2.5 Application Circuits
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
8.2.2.5.1 V-t Product Calculation

To prevent a transformer from saturation its V-t product must be greater than the maximum V-t product applied by the SN6501. The maximum voltage delivered by the SN6501 is the nominal converter input plus 10%. The maximum time this voltage is applied to the primary is half the period of the lowest frequency at the specified input voltage. Therefore, the transformer’s minimum V-t product is determined through:

Equation 3. GUID-990135D6-C907-4F64-A441-792B8408FB32-low.gif

Inserting the numeric values from the data sheet into the equation above yields the minimum V-t products of

Equation 4. GUID-70755199-27DA-45A8-86BF-2B087937B457-low.gif

Common V-t values for low-power center-tapped transformers range from 22 Vμs to 150 Vμs with typical footprints of 10 mm x 12 mm. However, transformers specifically designed for PCMCIA applications provide as little as 11 Vμs and come with a significantly reduced footprint of 6 mm x 6 mm only.

While Vt-wise all of these transformers can be driven by the SN6501, other important factors such as isolation voltage, transformer wattage, and turns ratio must be considered before making the final decision.