SLUS270G March   1999  – May 2020 UCC2800 , UCC2801 , UCC2802 , UCC2803 , UCC2804 , UCC2805

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
    1.     Pin Functions
  8. 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. 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 Support Resources
    2. 13.2 Trademarks
    3. 13.3 Electrostatic Discharge Caution
    4. 13.4 Glossary
    5. 13.5 Related Links
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

9.3.1.7 VCC

VCC is the power input connection for this device. In normal operation, VCC is powered through a current limiting resistor. Although quiescent VCC current is very low, total supply current is higher, depending on the OUT current. Total VCC current is the sum of quiescent VCC current and the average OUT current. Knowing the operating frequency and the MOSFET gate charge (Qg), average OUT current can be calculated from Equation 6.

Equation 6. GUID-9E24C5F3-8BE8-463E-99E1-E3B1A111E907-low.gif

The UCC280x has a lower VCC (supply voltage) clamp of 13.5 V typical versus 30 V on the UC3842. For applications that require a higher VCC voltage, a resistor must be placed in series with VCC to increase the source impedance. The maximum value of this resistor is calculated with Equation 7.

Equation 7. GUID-33FC38E1-3BF6-4EB4-8518-535628CED4E2-low.gif

In Equation 7, VIN(min) is the minimum voltage that is used to supply VCC, VVCC(max) is the maximum VCC clamp voltage and IVCC is the IC supply current without considering the gate driver current and Qg is the external power MOSFET gate charge and f is the switching frequency.

Additionally, the UCC280x has an on-chip Zener diode to regulate VCC to 13.5 V. The turnon and turnoff thresholds for the UCC280x family are significantly different: 12.5 V and 8 V for the UCC2802 and UCC2804;
4.1 V and 3.6 V for the UCC2803 and UCC2805. 5-V PWM operation is now possible. To ensure against noise related problems, filter VCC with an electrolytic and bypass with a ceramic capacitor to ground. Keep the capacitors close to the IC pins.