SLUS161F April   1999  – May 2020 UCC2813-0 , UCC2813-1 , UCC2813-2 , UCC2813-3 , UCC2813-4 , UCC2813-5 , UCC3813-0 , UCC3813-1 , UCC3813-2 , UCC3813-3 , UCC3813-4 , UCC3813-5

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
    1.     Device Images
      1.      Block Diagram
  4. Revision History
  5. Device Comparison Table
  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  Detailed Pin Descriptions
        1. 8.3.1.1 COMP
        2. 8.3.1.2 CS
        3. 8.3.1.3 FB
        4. 8.3.1.4 GND
        5. 8.3.1.5 OUT
        6. 8.3.1.6 RC
        7. 8.3.1.7 REF
        8. 8.3.1.8 VCC
      2. 8.3.2  Undervoltage Lockout (UVLO)
      3. 8.3.3  Self-Biasing, Active Low Output
      4. 8.3.4  Reference Voltage
      5. 8.3.5  Oscillator
      6. 8.3.6  Synchronization
      7. 8.3.7  PWM Generator
      8. 8.3.8  Minimum Off-Time Adjustment (Dead-Time Control)
      9. 8.3.9  Leading Edge Blanking
      10. 8.3.10 Minimum Pulse Width
      11. 8.3.11 Current Limiting
      12. 8.3.12 Overcurrent Protection and Full-Cycle Restart
      13. 8.3.13 Soft Start
      14. 8.3.14 Slope Compensation
    4. 8.4 Device Functional Modes
      1. 8.4.1 Normal Operation
      2. 8.4.2 UVLO Mode
      3. 8.4.3 Soft-Start Mode
      4. 8.4.4 Fault Mode
  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  Bulk Capacitor Calculation
        2. 9.2.2.2  Transformer Design
        3. 9.2.2.3  MOSFET and Output Diode Selection
        4. 9.2.2.4  Output Capacitor Calculation
        5. 9.2.2.5  Current Sensing Network
        6. 9.2.2.6  Gate Drive Resistor
        7. 9.2.2.7  REF Bypass Capacitor
        8. 9.2.2.8  RT and CT
        9. 9.2.2.9  Start-Up Circuit
        10. 9.2.2.10 Voltage Feedback Compensation Procedure
          1. 9.2.2.10.1 Power Stage Gain, Zeroes, and Poles
          2. 9.2.2.10.2 Compensating the Loop
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Related Links
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Community Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • D|8
  • P|8
  • PW|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Bulk Capacitor Calculation

The design starts with selecting an appropriate bulk capacitor.

The primary-side bulk capacitor is selected based on the input power level and on the desired minimum bulk voltage level. The bulk capacitor value can be calculated by Equation 5.

Equation 5. UCC2813-0 UCC2813-1 UCC2813-2 UCC2813-3 UCC2813-4 UCC2813-5 UCC3813-0 UCC3813-1 UCC3813-2 UCC3813-3 UCC3813-4 UCC3813-5 Equation_7_2_SLUS207E.gif

where

  • PIN is the maximum output power divided by the target efficiency at maximum load
  • VIN(min) is the minimum AC input voltage RMS value
  • VBULK(min) is the target minimum bulk voltage
  • fLINE is the line frequency

Based on this equation, to achieve 75-V minimum bulk voltage, assuming 85% converter efficiency and 47-Hz minimum line frequency, the bulk capacitor must be larger than 127 µF. 180 µF was chosen in the design, considering the typical tolerance of bulk capacitors.