SLUS873C January   2009  – December 2016 UC1825A-SP

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  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 Leading Edge Blanking
      2. 8.3.2 UVLO, Soft-Start, and Fault Management
      3. 8.3.3 Active Low Outputs During UVLO
      4. 8.3.4 Control Methods
      5. 8.3.5 Synchronization
      6. 8.3.6 High Current Outputs
      7. 8.3.7 Open Loop Test Circuit
    4. 8.4 Device Functional Modes
  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  Auxiliary Supply Voltage
        2. 9.2.2.2  Oscillator Frequency
        3. 9.2.2.3  Preliminary Considerations
        4. 9.2.2.4  Input Power
        5. 9.2.2.5  Primary Current
        6. 9.2.2.6  Sense Resistor R(s)
        7. 9.2.2.7  MOSFET DC Losses
        8. 9.2.2.8  Selection of Core Material
        9. 9.2.2.9  Main Transformer Design
        10. 9.2.2.10 Calculation of Transformer
        11. 9.2.2.11 Minimum Core Size
        12. 9.2.2.12 Core Loss Limited Conditions
        13. 9.2.2.13 Core Geometry Selection
        14. 9.2.2.14 Wire Size Selection
        15. 9.2.2.15 Calculate Secondary RMS Current
        16. 9.2.2.16 Transformer Assembly
        17. 9.2.2.17 Calculation of Winding Resistances and Losses
        18. 9.2.2.18 Transformer Power Losses
        19. 9.2.2.19 Output Section
          1. 9.2.2.19.1 Output Choke Calculations
          2. 9.2.2.19.2 Output Capacitor
          3. 9.2.2.19.3 Output Diodes
        20. 9.2.2.20 UC1825A-SP PWM Control Section
          1. 9.2.2.20.1 Current Limit and Shutdown
          2. 9.2.2.20.2 Ramp
          3. 9.2.2.20.3 Slope Compensation
        21. 9.2.2.21 Closing the Feedback Loop
          1. 9.2.2.21.1 Error Amplifier
          2. 9.2.2.21.2 Control to Output Gain
          3. 9.2.2.21.3 Error Amplifier Compensation
          4. 9.2.2.21.4 Dynamic Performance
          5. 9.2.2.21.5 Short Circuit
          6. 9.2.2.21.6 Circuit Power Losses
        22. 9.2.2.22 Summary
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Feedback Traces
      2. 11.1.2 Input/Output Capacitors
      3. 11.1.3 Compensation Components
      4. 11.1.4 Traces and Ground Planes
      5. 11.1.5 Ground Planes
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Community Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

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12 Device and Documentation Support

12.1 Device Support

12.1.1 Third-Party Products Disclaimer

TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.

12.2 Documentation Support

12.2.1 Related Documentation

For related documentation see the following:

  • Unitrode Application Note U-93, SLUA075.
  • Unitrode Application Note U-97, SLUA101.
  • Unitrode Application Note U-110, SLUA053.

12.3 Receiving Notification of Documentation Updates

To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper right corner, click on Alert me to register and receive a weekly digest of any product information that has changed. For change details, review the revision history included in any revised document.

12.4 Community Resources

The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use.

    TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers.
    Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support.

12.5 Trademarks

E2E is a trademark of Texas Instruments.

All other trademarks are the property of their respective owners.

12.6 Electrostatic Discharge Caution

esds-image

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates.

12.7 Glossary

SLYZ022 — TI Glossary.

This glossary lists and explains terms, acronyms, and definitions.