SLUSF78A June   2023  – November 2024 UCC28731-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
    1.     Pin Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Timing Requirements
    7. 5.7 Switching Characteristics
    8. 5.8 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Detailed Pin Description
        1. 6.3.1.1 VDD (Device Bias Voltage Supply)
        2. 6.3.1.2 GND (Ground)
        3. 6.3.1.3 HV (High Voltage Startup)
        4. 6.3.1.4 DRV (Gate Drive)
        5. 6.3.1.5 CBC (Cable Compensation)
        6. 6.3.1.6 VS (Voltage Sense)
        7. 6.3.1.7 CS (Current Sense)
      2. 6.3.2 Primary-Side Regulation (PSR)
      3. 6.3.3 Primary-Side Constant Voltage Regulation
      4. 6.3.4 Primary-Side Constant Current Regulation
      5. 6.3.5 Valley-Switching and Valley-Skipping
      6. 6.3.6 Startup Operation
      7. 6.3.7 Fault Protection
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Input Bulk Capacitance and Minimum Bulk Voltage
        2. 7.2.2.2 Transformer Turns Ratio, Inductance, Primary-Peak Current
        3. 7.2.2.3 Transformer Parameter Verification
        4. 7.2.2.4 Output Capacitance
        5. 7.2.2.5 VDD Capacitance, CVDD
        6. 7.2.2.6 VS Resistor Divider, Line Compensation, and Cable Compensation
      3. 7.2.3 Application Curves
    3. 7.3 Do's and Don'ts
    4. 7.4 Power Supply Recommendations
    5. 7.5 Layout
      1. 7.5.1 Layout Guidelines
      2. 7.5.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Device Nomenclature
        1. 8.1.1.1  Capacitance Terms in Farads
        2. 8.1.1.2  Duty-Cycle Terms
        3. 8.1.1.3  Frequency Terms in Hertz
        4. 8.1.1.4  Current Terms in Amperes
        5. 8.1.1.5  Current and Voltage Scaling Terms
        6. 8.1.1.6  Transformer Terms
        7. 8.1.1.7  Power Terms in Watts
        8. 8.1.1.8  Resistance Terms in Ω
        9. 8.1.1.9  Timing Terms in Seconds
        10. 8.1.1.10 DC Voltage Terms in Volts
        11. 8.1.1.11 AC Voltage Terms in Volts
        12. 8.1.1.12 Efficiency Terms
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

6.3.1.4 DRV (Gate Drive)

The DRV pin connects to the MOSFET gate pin, usually through a series resistor. The gate driver provides a gate-drive signal limited to 14V. The turn-on characteristic of the driver is a 29mA current source which limits the turn-on dv/dt of the MOSFET drain and reduces the leading-edge current spike, while still providing a gate-drive current to overcome the Miller plateau. The gate-drive turn-off current is determined by the RDS(on) of the low-side driver and any external gate drive resistance. Adding external gate resistance reduces the MOSFET drain turn-off dv/dt, if necessary. Such resistance value is generally higher than the typical 10Ω commonly used to damp resonance. However, calculation of the external resistance value to achieve a specific dv/dt involves MOSFET parameters beyond the scope of this datasheet.