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

3 Description

The UCC28731-Q1 isolated-flyback power supply controller provides constant-voltage (CV) and constant-current (CC) output regulation without the use of an optical coupler minimizing board area plus BOM count for higher lifetime reliability. This device processes information from the primary power switch and an auxiliary flyback winding for precise regulation of output voltage and current, hence the label "PSR".

A minimum switching frequency of 32Hz facilitates achieving less than 5mW of no-load power. An internal 700V start-up switch, dynamically- controlled operating states and a tailored modulation profile support ultra-low stand-by power without sacrificing start-up time. Control algorithms in the UCC28731-Q1 allow operating efficiencies to meet or exceed applicable standards. Discontinuous conduction mode (DCM) operation with valley-switching reduces switching losses. Modulation of the switching frequency and primary current peak amplitude (FM and AM) keeps the conversion efficiency high across the entire load and line ranges.

Device Information
PART NUMBER(1)PACKAGEBODY SIZE (NOM)

UCC28731QDRQ1

SOIC (7)4.90mm x 3.90mm
(1) For all available packages, see the orderable addendum at the end of the data sheet.
UCC28731-Q1 Simplified Schematic Figure 3-1 Simplified Schematic