SLUSG21A May   2025  – September 2025 UCC25661

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  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 Switching Characteristics
    7. 6.7 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Input Power Proportional Control
        1. 7.3.1.1 Voltage Feedforward
      2. 7.3.2 VCR Synthesizer
        1. 7.3.2.1 TSET Programming
      3. 7.3.3 Feedback Chain (Control Input)
      4. 7.3.4 Adaptive Dead-Time
      5. 7.3.5 Input Voltage Sensing
        1. 7.3.5.1 Brownin and Brownout Thresholds and Options
        2. 7.3.5.2 AC Input Zero Crossing Detection
        3. 7.3.5.3 Output OVP and External OTP
      6. 7.3.6 Resonant Tank Current Sensing
    4. 7.4 Protections
      1. 7.4.1 Zero Current Switching (ZCS) Protection
      2. 7.4.2 Minimum Current Turn-off During Soft Start
      3. 7.4.3 Cycle by Cycle Current Limit and Short Circuit Protection
      4. 7.4.4 Overload (OLP) Protection
      5. 7.4.5 VCC OVP Protection
    5. 7.5 Device Functional Modes
      1. 7.5.1 Startup
        1. 7.5.1.1 With HV Start-up
          1. 7.5.1.1.1 First Time Start-up Sequence
          2. 7.5.1.1.2 Restart Sequence
        2. 7.5.1.2 Without HV Startup
      2. 7.5.2 Soft Start Ramp
        1. 7.5.2.1 Startup Transition to Regulation
      3. 7.5.3 Light Load Management
        1. 7.5.3.1 Operating Modes (Burst Pattern)
        2. 7.5.3.2 Mode Transition Management
        3. 7.5.3.3 Burst Mode Thresholds Programming
  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  LLC Power Stage Requirements
        2. 8.2.2.2  LLC Gain Range
        3. 8.2.2.3  Select Ln and Qe
        4. 8.2.2.4  Determine Equivalent Load Resistance
        5. 8.2.2.5  Determine Component Parameters for LLC Resonant Circuit
        6. 8.2.2.6  LLC Primary-Side Currents
        7. 8.2.2.7  LLC Secondary-Side Currents
        8. 8.2.2.8  LLC Transformer
        9. 8.2.2.9  LLC Resonant Inductor
        10. 8.2.2.10 LLC Resonant Capacitor
        11. 8.2.2.11 LLC Primary-Side MOSFETs
        12. 8.2.2.12 Design Considerations for Adaptive Dead-Time
        13. 8.2.2.13 LLC Rectifier Diodes
        14. 8.2.2.14 LLC Output Capacitors
        15. 8.2.2.15 HV Pin Series Resistors
        16. 8.2.2.16 BLK Pin Voltage Divider
        17. 8.2.2.17 ISNS Pin Differentiator
        18. 8.2.2.18 TSET Pin
        19. 8.2.2.19 OVP/OTP Pin
        20. 8.2.2.20 Burst Mode Programming
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
      1. 8.3.1 VCCP Pin Capacitor
      2. 8.3.2 Boot Capacitor
      3. 8.3.3 V5P Pin Capacitor
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
        1. 8.4.2.1 Schematics
  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

7.1 Overview

The UCC25661 is a fully featured LLC resonant controller for isolated power supplies. UCC25661 incorporates high levels of integration and several design features to accommodate wide input and output voltage operation, high power density, and increased reliability of the LLC power stage.

The device novel control scheme input power proportional control (IPPC) offers excellent transient performance inherent in the current mode controls, while enabling a linear relationship between input power and control signal across wide input and output voltage variation. The IPPC control enables consistent light load, burst mode performance operation across a wide input and output voltage variation.

Some of the new features in UCC25661 are specified below:

  • IPPC Control enables more stable burst mode and dynamic response under wide input/output voltage operation
  • New operation modes to increase light load efficiency while reducing audible noise
    • High-frequency (HF) pulse skip for improved light load efficiency
    • Low-frequency (LF) burst mode for reduced stand by power consumption
    • Programmable light load/burst mode thresholds to balance output ripple and efficiency
    • Adaptive burst mode threshold adjustment to accommodate input voltage change
    • Wide burst mode hysteresis to prevent oscillating in and out of burst mode
    • Soft in and soft out of burst mode to further minimize audible noise plus option to force retention of burst mode
  • Full-load switching frequency enables high power density designs: up to 750kHz
  • Combined resonant current sensing with internal control voltage generation, improves control robustness
  • Input voltage feed forward
  • Integrated protections include:
    • Fast cycle-by-cycle current limiting: 50ns
    • OCP fault to protect under short circuit conditions
    • Over Power Protection (OPP) to limit peak input power
    • Zero Current Switching (ZCS) avoidance scheme to eliminate capacitive region operation
    • Adaptive soft start for reduced inrush current and eliminating reverse recovery at start-up
    • External OVP/OTP protection
    • Input and bias supply (VCCP) UVLO
    • Input voltage feed forward
    • OCP/OLP decoupling allows protection thresholds sets independently
UCC25661 Simplified Application SchematicFigure 7-1 Simplified Application Schematic