SLUS794F November   2007  – April 2016 UCC28070

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Interleaving
      2. 7.3.2  Programming the PWM Frequency and Maximum Duty-Cycle Clamp
      3. 7.3.3  Frequency Dithering (Magnitude and Rate)
      4. 7.3.4  External Clock Synchronization
      5. 7.3.5  Multi-phase Operation
      6. 7.3.6  VSENSE and VINAC Resistor Configuration
      7. 7.3.7  VSENSE and VINAC Open-Circuit Protection
      8. 7.3.8  Current Synthesizer
      9. 7.3.9  Programmable Peak Current Limit
      10. 7.3.10 Linear Multiplier and Quantized Voltage Feed Forward
      11. 7.3.11 Enhanced Transient Response (VA Slew-Rate Correction)
      12. 7.3.12 Voltage Biasing (VCC and VVREF)
      13. 7.3.13 PFC Enable and Disable
      14. 7.3.14 Adaptive Soft Start
      15. 7.3.15 PFC Start-Up Hold Off
      16. 7.3.16 Output Overvoltage Protection (OVP)
      17. 7.3.17 Zero-Power Detection
      18. 7.3.18 Thermal Shutdown
      19. 7.3.19 Current Loop Compensation
      20. 7.3.20 Voltage Loop Compensation
    4. 7.4 Device Functional Modes
  8. 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 Output Current Calculation
        2. 8.2.2.2 Bridge Rectifier
        3. 8.2.2.3 PFC Inductor (L1 and L2)
        4. 8.2.2.4 PFC MOSFETs (M1 and M2)
        5. 8.2.2.5 PFC Diode
        6. 8.2.2.6 PFC Output Capacitor
        7. 8.2.2.7 Current Loop Feedback Configuration (Sizing of the Current Transformer Turns Ratio and Sense Resistor (RS)
        8. 8.2.2.8 Current Sense Offset and PWM Ramp for Improved Noise Immunity
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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9 Power Supply Recommendations

The UCC28070 should be operated from a VCC rail which is within the limits given in Recommended Operating Conditions. To avoid the possibility that the device might stop switching, VCC must not be allowed to fall into the UVLO range.

In order to minimize power dissipation in the device, VCC should not be unnecessarily high. Keeping VCC at 12 V is a good compromise between these competing constraints.

The gate drive outputs from the UCC28070 can deliver large current pulses into their loads. This indicates the need for a low ESR decoupling capacitor to be connected as directly as possible between the VCC and GND pins. TI recommends ceramic capacitors with a stable dielectric characteristic over temperature, such as X7R. Avoid capacitors which have a large drop in capacitance with applied DC voltage bias and use a part that has a low voltage co-efficient of capacitance. TI recommends a decoupling capacitance of 10 μF, X7R, with at least a 25-V rating. A capacitor of at least 0.1 μF must be placed as close as possible between the VCC and GND pins.