SLUSAO7C September   2011  – July 2024 UCC28063

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Revision History
  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 Feature Description
      1. 7.3.1  Principles of Operation
      2. 7.3.2  Natural Interleaving
      3. 7.3.3  On-Time Control, Maximum Frequency Limiting, and Restart Timer
      4. 7.3.4  Distortion Reduction
      5. 7.3.5  Zero-Current Detection and Valley Switching
      6. 7.3.6  Phase Management and Light-Load Operation
      7. 7.3.7  External Disable
      8. 7.3.8  Improved Error Amplifier
      9. 7.3.9  Soft Start
      10. 7.3.10 Brownout Protection
      11. 7.3.11 Dropout Detection
      12. 7.3.12 VREF
      13. 7.3.13 VCC
      14. 7.3.14 Control of Downstream Converter
      15. 7.3.15 System Level Protections
        1. 7.3.15.1 Failsafe OVP - Output Overvoltage Protection
        2. 7.3.15.2 Overcurrent Protection
        3. 7.3.15.3 Open-Loop Protection
        4. 7.3.15.4 VCC Undervoltage Lock-Out (UVLO) Protection
        5. 7.3.15.5 Phase-Fail Protection
        6. 7.3.15.6 CS-Open, TSET-Open and -Short Protection
        7. 7.3.15.7 Thermal Shutdown Protection
        8. 7.3.15.8 AC-Line Brownout and Dropout Protections
        9. 7.3.15.9 Fault Logic Diagram
    4. 7.4 Device Functional Modes
  9. 8 Applications 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  Inductor Selection
        2. 8.2.2.2  ZCD Resistor Selection (RZA, RZB)
        3. 8.2.2.3  HVSEN
        4. 8.2.2.4  Output Capacitor Selection
        5. 8.2.2.5  Selecting (RS) For Peak Current Limiting
        6. 8.2.2.6  Power Semiconductor Selection (Q1, Q2, D1, D2)
        7. 8.2.2.7  Brownout Protection
        8. 8.2.2.8  Converter Timing
        9. 8.2.2.9  Programming VOUT
        10. 8.2.2.10 Voltage Loop Compensation
      3. 8.2.3 Application Curves
        1. 8.2.3.1 Input Ripple Current Cancellation with Natural Interleaving
        2. 8.2.3.2 Brownout Protection
  10. 9 Power Supply Recommendations
  11. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Related Parts
      2. 11.1.2 Device Nomenclature
        1. 11.1.2.1 Detailed Pin Description
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  13. 12Mechanical, Packaging, and Orderable Information

8.2.2.7 Brownout Protection

Resistor RA and RB are selected to activate brownout protection at ~75% of the specified minimum-operating input voltage. Resistor RA programs the brownout hysteresis comparator, which is selected to provide 17 V (~12 VRMS) of hysteresis. Calculations for RA and RB are shown in Equation 44 through Equation 47.

Equation 44. UCC28063

To meet voltage requirements, three 2.87-MΩ resistors were used in series for RA.

Equation 45. UCC28063
Equation 46. UCC28063

Select a standard value for RB.

Equation 47. UCC28063

In this design example, brownout becomes active (shuts down PFC) when the input drops below 66 VRMS for longer than 440 ms and deactivates (restarts with a full soft start) when the input reaches 78 VRMS.