SLLSFW9 April   2024 ISO7741TA-Q1

ADVANCE INFORMATION  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
    1.     Pin Functions
  6. 5 Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  ESD Ratings
    3. 5.3  Recommended Operating Conditions
    4. 5.4  Thermal Information
    5. 5.5  Power Ratings
    6. 5.6  Insulation Specifications
    7. 5.7  Safety-Related Certifications
    8. 5.8  Safety Limiting Values
    9. 5.9  Electrical Characteristics Transformer
    10. 5.10 Electrical Characteristics—5-V Supply
    11. 5.11 Supply Current Characteristics—5-V Supply
    12. 5.12 Electrical Characteristics—3.3-V Supply
    13. 5.13 Supply Current Characteristics—3.3-V Supply
    14. 5.14 Electrical Characteristics—2.5-V Supply 
    15. 5.15 Supply Current Characteristics—2.5-V Supply
    16. 5.16 Switching Characteristics—5-V Supply
    17. 5.17 Switching Characteristics—3.3-V Supply
    18. 5.18 Switching Characteristics—2.5-V Supply
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Electromagnetic Compatibility (EMC) Considerations
      2. 6.3.2 Push-Pull Converter
      3. 6.3.3 Core Magnetization
    4. 6.4 Device Functional Modes
      1. 6.4.1 Device I/O Schematics
      2. 6.4.2 Start-Up Mode
      3. 6.4.3 Operating Mode
      4. 6.4.4 Spread Spectrum Clocking
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Drive Capability
        2. 7.2.2.2 LDO Selection
        3. 7.2.2.3 Diode Selection
        4. 7.2.2.4 Capacitor Selection
        5. 7.2.2.5 Transformer Selection
          1. 7.2.2.5.1 V-t Product Calculation
          2. 7.2.2.5.2 Turns Ratio Estimate
          3. 7.2.2.5.3 Recommended Transformers
      3. 7.2.3 Application Curve
        1. 7.2.3.1 Insulation Lifetime
      4. 7.2.4 System Examples
        1. 7.2.4.1 Higher Output Voltage Designs
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • DW|16
Thermal pad, mechanical data (Package|Pins)
Orderable Information
7.2.2.5.1 V-t Product Calculation

To prevent a transformer from saturation, the V-t product must be greater than the maximum V-t product applied by the device. The maximum voltage delivered by the device 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 minimum V-t product for the transformer is determined through:

Equation 3. V t m i n ≥ V I N - m a x × T m a x 2 = V I N - m a x 2 × f m i n

Taking an example of fmin as 138kHz for ISO7741TA-Q1 and 363kHZ for ISO7741TB-Q1 with a 5V supply, the following equations yield the minimum V-t products of:

V t m i n ≥ 5.5 V 2 × 138 k H z = 20 V μ s for ISO7741TA-Q1 applications, and
V t m i n ≥ 5.5 V 2 × 363 k H z = 7.6 V μ s for ISO7741TB-Q1 applications

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

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