SGLS121D December   2002  – June 2020 UCC2800-Q1 , UCC2801-Q1 , UCC2802-Q1 , UCC2803-Q1 , UCC2804-Q1 , UCC2805-Q1

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
    1.     Device Images
      1.      Simplified Application Diagram
  4. Revision History
  5. Description (continued)
  6. Device Comparison Table
  7. Pin Configuration and Functions
    1.     Pin Functions
  8. Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Typical Characteristics
  9. Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1  Detailed Pin Description
        1. 9.3.1.1 COMP
        2. 9.3.1.2 FB
        3. 9.3.1.3 CS
        4. 9.3.1.4 RC
        5. 9.3.1.5 GND
        6. 9.3.1.6 OUT
        7. 9.3.1.7 VCC
        8. 9.3.1.8 Pin 8 (REF)
      2. 9.3.2  Undervoltage Lockout (UVLO)
      3. 9.3.3  Self-Biasing, Active Low Output
      4. 9.3.4  Reference Voltage
      5. 9.3.5  Oscillator
      6. 9.3.6  Synchronization
      7. 9.3.7  PWM Generator
      8. 9.3.8  Minimum Off-Time Setting (Dead-Time Control)
      9. 9.3.9  Leading Edge Blanking
      10. 9.3.10 Minimum Pulse Width
      11. 9.3.11 Current Limiting
      12. 9.3.12 Overcurrent Protection and Full Cycle Restart
      13. 9.3.13 Soft Start
      14. 9.3.14 Slope Compensation
    4. 9.4 Device Functional Modes
      1. 9.4.1 Normal Operation
      2. 9.4.2 UVLO Mode
      3. 9.4.3 Soft Start Mode
      4. 9.4.4 Fault Mode
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Current Sensing Network
        2. 10.2.2.2 Gate Drive Resistor
        3. 10.2.2.3 Vref Capacitor
        4. 10.2.2.4 RTCT
        5. 10.2.2.5 Start-Up Circuit
        6. 10.2.2.6 Voltage Feedback Compensation
          1. 10.2.2.6.1 Power Stage Gain, Zeroes, and Poles
          2. 10.2.2.6.2 Compensation Loop
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Community Resources
    2. 13.2 Trademarks
    3. 13.3 Related Links
    4. 13.4 Electrostatic Discharge Caution
    5. 13.5 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • D|8
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Minimum Off-Time Setting (Dead-Time Control)

Dead time is the term used to describe the ensured OFF time of the PWM output during each oscillator cycle. It is used to ensure that even at maximum duty cycle, there is enough time to reset the magnetic circuit elements, and prevent saturation. The dead time of the UCC280x-Q1 PWM family is determined by the internal 130-Ω discharge impedance and the timing capacitor value. Larger capacitance values extend the dead time whereas smaller values results in higher maximum duty cycles for the same operating frequency. A curve for dead time versus timing capacitor values is provided in Figure 20. Increasing the dead time is possible by adding a resistor between the RC pin of the IC and the timing components, as shown in Figure 21. The dead time increases with the discharge resistor value to about 470 Ω as indicated from the curve in Figure 22. Higher resistances must be avoided as they can decrease the dead time and reduce the oscillator peak-to-peak amplitude. Sinking too much current (1 mA) by reducing RT will freeze the oscillator OFF by preventing discharge to the lower comparator threshold voltage of 0.2 V. Adding this discharge control resistor has several impacts on the oscillator programming. First, it introduces a DC offset to the capacitor during the discharge – but not the charging portion of the timing cycle, thus lowering the usable peak-to-peak timing capacitor amplitude. Because of the reduced peak-to-peak amplitude, the exact value of CT may require adjustment from UC3842 type designs to obtain the correct initial oscillator frequency. One alternative is keep the same value timing capacitor and adjust both the timing and discharge resistor values because these are readily available in finer numerical increments.

UCC2800-Q1 UCC2801-Q1 UCC2802-Q1 UCC2803-Q1 UCC2804-Q1 UCC2805-Q1 u133-11.gifFigure 20. Minimum Dead Time vs CT
UCC2800-Q1 UCC2801-Q1 UCC2802-Q1 UCC2803-Q1 UCC2804-Q1 UCC2805-Q1 u133_13.gifFigure 21. Circuit to Produce Controlled
Maximum Duty Cycle
UCC2800-Q1 UCC2801-Q1 UCC2802-Q1 UCC2803-Q1 UCC2804-Q1 UCC2805-Q1 MaxDuty.gifFigure 22. Maximum Duty Cycle vs RD for RT = 20 kΩ