SLUSFF2 October   2024 UCG28826

ADVANCE INFORMATION  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and 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 Electrical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Detailed Pin Descriptions
      1. 6.3.1  HV - High Voltage Input
      2. 6.3.2  SW - Switch Node
      3. 6.3.3  GND – Ground Return
      4. 6.3.4  FLT - External Overtemperature Fault
      5. 6.3.5  FB ­­– Feedback
      6. 6.3.6  TR - Turns Ratio
      7. 6.3.7  IPK - Peak Current and Dithering
      8. 6.3.8  FCL - Frequency clamp and fault response
      9. 6.3.9  CDX - CCM, drive strength and X-cap discharge
      10. 6.3.10 VCC - Input Bias
    4. 6.4 Feature Description
      1. 6.4.1  Self Bias and Auxless Sensing
      2. 6.4.2  Control Law
        1. 6.4.2.1 Valley Switching
        2. 6.4.2.2 Frequency Foldback
        3. 6.4.2.3 Burst Mode
        4. 6.4.2.4 Continuous Conduction Mode (CCM)
      3. 6.4.3  GaN HEMT Switching Capability
      4. 6.4.4  Soft Start
      5. 6.4.5  Frequency Clamp
      6. 6.4.6  Frequency Dithering
      7. 6.4.7  Slew Rate Control
      8. 6.4.8  Transient Peak Power Capability
      9. 6.4.9  X-Cap Discharge
      10. 6.4.10 Fault Protections
        1. 6.4.10.1 Brownout Protection
        2. 6.4.10.2 Short-Circuit Protection
        3. 6.4.10.3 Output Over Voltage Protection
        4. 6.4.10.4 Over Power Protection (OPP, LPS)
        5. 6.4.10.5 Overtemperature Protection
        6. 6.4.10.6 Open FB Protection
        7. 6.4.10.7 Error Codes for Protections
  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 Input Bulk Capacitor
        2. 7.2.2.2 Transformer Primary Inductance and Turns Ratio
        3. 7.2.2.3 Output Capacitor
        4. 7.2.2.4 Selection Resistors
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information
    1. 10.1 Package Option Addendum
    2. 10.2 Mechanical Data

6.4.10.2 Short-Circuit Protection

The UCG28826 includes an overcurrent protection circuit to detect and prevent damage during overload conditions. This can occur during short-circuit of transformer windings, SR FET drain-source terminals or the flyback converter output. The device detects primary currents exceeding 4.5A (typ.) immediately after primary GaN HEMT turn-on and expiration of the leading edge blanking (LEB) time for SW node capacitance discharge to GND. If short-circuit current threshold is triggered for three consecutive cycles, a short-circuit fault is declared and switching stops. Fault response, auto-retry or latch, is as per selection with resistor on FCL pin.