SLUSC60B December   2017  – October 2019 UCC28064A

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
    1.     Device Images
      1.      Simplified Application
  4. Revision History
  5. Description (Continued)
  6. Pin Configuration and Functions
    1.     Pin Functions
  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. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Principles of Operation
      2. 8.3.2  Natural Interleaving
      3. 8.3.3  On-Time Control, Maximum Frequency Limiting, Restart Timer and Input Voltage Feed-Forward compensation
      4. 8.3.4  Distortion Reduction
      5. 8.3.5  Zero-Current Detection and Valley Switching
      6. 8.3.6  Phase Management and Light-Load Operation
      7. 8.3.7  Burst Mode Operation
      8. 8.3.8  External Disable
      9. 8.3.9  Improved Error Amplifier
      10. 8.3.10 Soft Start
      11. 8.3.11 Brownout Protection
      12. 8.3.12 Line Dropout Detection
      13. 8.3.13 VREF
      14. 8.3.14 VCC
      15. 8.3.15 System Level Protections
        1. 8.3.15.1 Failsafe OVP - Output Over-voltage Protection
        2. 8.3.15.2 Overcurrent Protection
        3. 8.3.15.3 Open-Loop Protection
        4. 8.3.15.4 VCC Undervoltage Lock-Out (UVLO) Protection
        5. 8.3.15.5 Phase-Fail Protection
        6. 8.3.15.6 CS - Open, TSET - Open and Short Protection
        7. 8.3.15.7 Thermal Shutdown Protection
        8. 8.3.15.8 Fault Logic Diagram
    4. 8.4 Device Functional Modes
  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  Custom Design With WEBENCH® Tools
        2. 9.2.2.2  Inductor Selection
        3. 9.2.2.3  ZCD Resistor Selection RZA, RZB
        4. 9.2.2.4  HVSEN
        5. 9.2.2.5  Output Capacitor Selection
        6. 9.2.2.6  Selecting RS For Peak Current Limiting
        7. 9.2.2.7  Power Semiconductor Selection (Q1, Q2, D1, D2)
        8. 9.2.2.8  Brownout Protection
        9. 9.2.2.9  Converter Timing
        10. 9.2.2.10 Programming VOUT
        11. 9.2.2.11 Voltage Loop Compensation
      3. 9.2.3 Application Curves
        1. 9.2.3.1 Input Ripple Current Cancellation with Natural Interleaving
        2. 9.2.3.2 Brownout Protection
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Package Option Addendum
    1. 12.1 Packaging Information
  13. 13Device and Documentation Support
    1. 13.1 Device Support
      1. 13.1.1 Development Support
        1. 13.1.1.1 Custom Design With WEBENCH® Tools
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Receiving Notification of Documentation Updates
    4. 13.4 Community Resources
    5. 13.5 Trademarks
    6. 13.6 Electrostatic Discharge Caution
    7. 13.7 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Inductor Selection

The boost inductor is selected based on the minimum switching requirements. Operating at the boundary between DCM and CCM the minimum switching frequency will be at maximum power and at the peak of the line. It is possible that the minimum switching frequency can occur at minimum line or at maximum line. Equation 20.

Equation 19. UCC28064A eq-17-SLUAGRV.gif
Equation 20. UCC28064A eq-18-SLUAGRV.gif

In order to be sure that converters operates always above the desired (fMIN) we will select the minimum value between LH that would be the value we have if we consider the minimum occurs at maximum input voltage and LL that would be the value we have if we consider that minimum switching frequency occurs at minimum Line voltage. For this design example, fMIN is set to 27 kHz in order to be always above the audible range. For a 2-phase interleaved design, L1 and L2 are determined by minimum between LH and LLas stated in formula (19) here belowEquation 21.

Equation 21. UCC28064A eq-20-SLUAGRV.gif

The inductor for this design would have a peak current (ILPEAK) of 5.4 A, as shown in Equation 22, and an RMS current (ILRMS) of 2.2 A, as shown in Equation 23.

Equation 22. UCC28064A qu20_lusao7.gif
Equation 23. UCC28064A qu21_lusao7.gif

This converter uses constant on time (TON) and zero-current detection (ZCD) to set up the converter timing. Auxiliary windings on L1 and L2 detect when the inductor currents are zero. Selecting the turns ratio using Equation 24 ensures that there will be at least 2 V at the peak of high line to reset the ZCD comparator after every switching cycle.

The turns-ratio of each auxiliary winding is:

Equation 24. UCC28064A qu22_lusao7.gif