SLUSFF2C September   2023  – December 2025 UCG28826 , UCG28828

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 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 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Detailed Pin Descriptions
      1. 7.3.1  HV - High Voltage Input
      2. 7.3.2  SW - Switch Node
      3. 7.3.3  GND – Ground Return
      4. 7.3.4  FLT - External Overtemperature Fault
      5. 7.3.5  FB ­­– Feedback
      6. 7.3.6  TR - Turns Ratio
      7. 7.3.7  IPK - Peak Current and Dithering
      8. 7.3.8  FCL - Frequency Clamp and Fault Response
      9. 7.3.9  CDX - CCM, Drive Strength, and X-cap Discharge
      10. 7.3.10 VCC - Input Bias
    4. 7.4 Feature Description
      1. 7.4.1  Self Bias and Auxless Sensing
      2. 7.4.2  Control Law
        1. 7.4.2.1 Valley Switching
        2. 7.4.2.2 Frequency Foldback
        3. 7.4.2.3 Burst Mode
        4. 7.4.2.4 Continuous Conduction Mode (CCM)
      3. 7.4.3  GaN HEMT Switching Capability
      4. 7.4.4  Soft Start
      5. 7.4.5  Frequency Clamp
      6. 7.4.6  Frequency Dithering
      7. 7.4.7  Slew Rate Control
      8. 7.4.8  Transient Peak Power Capability
      9. 7.4.9  X-Cap Discharge
      10. 7.4.10 Fault Protections
        1. 7.4.10.1 Brownout Protection
        2. 7.4.10.2 Short-Circuit Protection
        3. 7.4.10.3 Output Overvoltage Protection
        4. 7.4.10.4 Overpower Protection (OPP, LPS)
        5. 7.4.10.5 Overtemperature Protection
        6. 7.4.10.6 Open FB Protection
        7. 7.4.10.7 Error Codes for Protections
  9. 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 Input Bulk Capacitor
        2. 8.2.2.2 Transformer Primary Inductance and Turns Ratio
        3. 8.2.2.3 Output Capacitor
        4. 8.2.2.4 Selection Resistors
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

8.3 Power Supply Recommendations

The UCG2882x is intended for use in AC/DC adapters with universal AC input in the range from 85VAC to 264VAC, 45Hz to 66Hz, using flyback topology for up to 65W output. While the UCG2882x is useful for USB-PD charger applications, this converter is also used in industrial applications with fixed output voltages at 12V, 24V, 36V, and so on. Change the TR pin resistor to accommodate output voltages that are different from the default 20V maximum output voltage setting. On the secondary side feedback, achieve output regulation with a USB-PD controller or TL431 for fixed output designs.

UCG2882x uses self-biasing technology, eliminates the need for Flyback auxiliary winding, reduces BoM cost, improves the efficiency, and simplifies the EMI design. The VCC voltage is self-regulated up to VVCC(REG) level. To provide proper function of the self-biasing mechanism place a high-frequency, low-ESL 0.1μF ceramic capacitor within 1mm of the VCC and GND pins.

Additionally, the overall VCC capacitance is selected based on the line frequency and line drop out test requirement. To minimize the converter standby power, the VCC capacitor must hold enough energy to provide the UCG2882x supply current in burst mode (IVCCSLEEP) through out half a line cycle. If the power supply must pass a line drop out test, VCC capacitor must hold enough energy to provide the supply current in burst mode (IVCCSLEEP), and through out the line drop-out period. The VCC capacitance is determined by the larger holdup time required for burst mode operation or line drop-out test. Follow Equation 13 to select the corresponding capacitor value. Because the capacitance reduces with voltage applied, perform capacitance derating.

Equation 13. CVCC>Tholdup×IVCCSLEEP÷0.3V