SLUSBE8B May   2013  – September 2015 UCC28720

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 Detailed Pin Description
    4. 7.4 Device Functional Modes
      1. 7.4.1 Primary-Side Voltage Regulation
      2. 7.4.2 Primary-Side Current Regulation
      3. 7.4.3 Valley Switching
      4. 7.4.4 Start-Up Operation
      5. 7.4.5 Fault Protection
  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 Stand-by Power Estimate
        2. 8.2.2.2 Input Bulk Capacitance and Minimum Bulk Voltage
        3. 8.2.2.3 Transformer Turns Ratio, Inductance, Primary-Peak Current
        4. 8.2.2.4 Transformer Parameter Verification
        5. 8.2.2.5 Output Capacitance
        6. 8.2.2.6 VDD Capacitance, CDD
        7. 8.2.2.7 VS Resistor Divider, Line Compensation, and Cable Compensation
      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 Device Support
      1. 11.1.1 Device Nomenclature
        1. 11.1.1.1 Definition of Terms
          1. 11.1.1.1.1  Capacitance Terms in Farads
          2. 11.1.1.1.2  Duty Cycle Terms
          3. 11.1.1.1.3  Frequency Terms in Hertz
          4. 11.1.1.1.4  Current Terms in Amperes
          5. 11.1.1.1.5  Current and Voltage Scaling Terms
          6. 11.1.1.1.6  Transformer Terms
          7. 11.1.1.1.7  Power Terms in Watts
          8. 11.1.1.1.8  Resistance Terms in Ω
          9. 11.1.1.1.9  Timing Terms in Seconds
          10. 11.1.1.1.10 Voltage Terms in Volts
          11. 11.1.1.1.11 AC Voltage Terms in VRMS
          12. 11.1.1.1.12 Efficiency Terms
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

10 Layout

10.1 Layout Guidelines

  • High frequency bypass Capacitor C5 must be placed across Pin 1 and 4 as close as you can get it to the pins.
  • Resistor R4 and C5 form a low pass filter and the connection of R4 and C5 must be as close to the VDD pin as possible.
  • The VS pin controls the output voltage through the transformer turns ratio and the voltage divider of R5 and R11. Note the trace length between the R5, R11 and VS pin should be as short as possible to reduce or eliminate possible EMI coupling.
  • The IC ground and power ground must meet at the bulk capacitor’s (C6 and C7) return. Try to ensure that high frequency/high current from the power stage does not go through the signal ground.
    • o The high frequency/high current path that you need to be cautious of on the primary is C7 +, T1 (P5, P3), Q1d, Q1s, R8 to the return of C6 and C7. Try to keep all high current loops as short as possible.
  • Try to keep all high current loops as short as possible.
  • Keep all high current/high frequency traces away from or perpendicular to other traces in the design.
  • Traces on the voltage clamp formed by D1, R2, D3 and C2 as short as possible.
  • C6 return needs to be as close to the bulk capacitor supply as possible. This reduces the magnitude of dv/dt caused by large di/dt.
  • Avoid mounting semiconductors under magnetics.

10.2 Layout Example

UCC28720 Layout_SLUSBE8.gif Figure 29. Layout
UCC28720 schem_lusbe8.gif Figure 30. 5W USB Adapter Schematic