SLUSDD5A April   2019  – December 2020 UC1825B-SP

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 Control Methods
      2. 7.3.2 Synchronization
      3. 7.3.3 High Current Outputs
      4. 7.3.4 Open Loop Test Circuit
    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 System Design Theory
        1. 8.2.1.1 Switching Frequency
        2. 8.2.1.2 Transformer
        3. 8.2.1.3 RCD and Diode Clamp
        4. 8.2.1.4 Output Diode
        5. 8.2.1.5 Main Switching MOSFETs
        6. 8.2.1.6 Output Filter and Capacitance
        7. 8.2.1.7 Compensation
        8. 8.2.1.8 Sense Resistor
    3. 8.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Feedback Traces
      2. 10.1.2 Input/Output Capacitors
      3. 10.1.3 Compensation Components
      4. 10.1.4 Traces and Ground Planes
      5. 10.1.5 Ground Planes
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support 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

7.4 Device Functional Modes

The UC1825B-SP is compatible with voltage-mode or current-mode topologies. The UC1825B-SP uses fixed frequency, peak current mode control. An internal oscillator initiates the turn-on of the driver to high-side power switch. The external power switch current is sensed through an external resistor and is compared through internal comparator. The voltage generated at the COMP pin is stepped down through internal resistors. When the sensed current reaches the stepped down COMP voltage, the high-side power switch is turned off.