SLUS270H March   1999  – April 2025 UCC1801 , UCC1802 , UCC1803 , UCC1804 , UCC1805 , UCC2800 , UCC2801 , UCC2802 , UCC2803 , UCC2804 , UCC2805 , UCC3800 , UCC3801 , UCC3802 , UCC3803 , UCC3804 , UCC3805

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration and Functions
  7. 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
  8. 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
        1. 7.3.1.1 COMP
        2. 7.3.1.2 FB
        3. 7.3.1.3 CS
        4. 7.3.1.4 RC
        5. 7.3.1.5 GND
        6. 7.3.1.6 OUT
        7. 7.3.1.7 VCC
        8. 7.3.1.8 Pin 8 (REF)
      2. 7.3.2  Undervoltage Lockout (UVLO)
      3. 7.3.3  Self-Biasing, Active Low Output
      4. 7.3.4  Reference Voltage
      5. 7.3.5  Oscillator
      6. 7.3.6  Synchronization
      7. 7.3.7  PWM Generator
      8. 7.3.8  Minimum Off-Time Setting (Dead-Time Control)
      9. 7.3.9  Leading Edge Blanking
      10. 7.3.10 Minimum Pulse Width
      11. 7.3.11 Current Limiting
      12. 7.3.12 Overcurrent Protection and Full Cycle Restart
      13. 7.3.13 Soft Start
      14. 7.3.14 Slope Compensation
    4. 7.4 Device Functional Modes
      1. 7.4.1 Normal Operation
      2. 7.4.2 UVLO Mode
      3. 7.4.3 Soft Start Mode
      4. 7.4.4 Fault Mode
  9. 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 Current Sensing Network
        2. 8.2.2.2 Gate Drive Resistor
        3. 8.2.2.3 Vref Capacitor
        4. 8.2.2.4 RTCT
        5. 8.2.2.5 Start-Up Circuit
        6. 8.2.2.6 Voltage Feedback Compensation
          1. 8.2.2.6.1 Power Stage Gain, Zeroes, and Poles
          2. 8.2.2.6.2 Compensation Loop
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Related Links
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2.4 RTCT

The internal oscillator uses a timing capacitor (CT) and a timing resistor (RT) to program operating frequency and maximum duty cycle. The operating frequency can be programmed based the curves in Figure 6-3, where the timing resistor can be found once the timing capacitor is selected. The selection of timing capacitor also affects the maximum duty cycle provided in Figure 6-5. It is best for the timing capacitor to have a flat temperature coefficient, typical of most COG or NPO type capacitors. For this converter, 13.6 kΩ and 1000 pF were selected for RT and CT to operate at 110-kHz switching.