SGLS183C August   2003  – July 2025 UCC2808A-1Q1 , UCC2808A-2Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configurations 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 Pin Descriptions
        1. 7.3.1.1 COMP Pin
        2. 7.3.1.2 OUTA and OUTB Pins
        3. 7.3.1.3 RC Pin
        4. 7.3.1.4 VDD Pin
    4. 7.4 Device Functional Modes
      1. 7.4.1 VCC
      2. 7.4.2 Push-Pull or Half-Bridge Function
  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
      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 Documentation Support
      1. 9.1.1 Related Documentation
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, 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

8.2.2 Detailed Design Procedure

The output, VO, provides 5V at 50W maximum and is electrically isolated from the input. Because the UCC2808A-1Q1 is a peak current mode controller, the 2N2907 emitter-follower amplifier buffers the oscillator waveform (RC pin) and provides slope compensation to the current sense (CS) input. This configuration is necessary for duty cycle ratios greater than 50%.

Capacitor decoupling is provided on the VDD pin. TI recommends using a minimum decoupling capacitance of 10µF electrolytic and 0.1µF ceramic. Place the ceramic capacitor as close to the VDD pin as possible. The UCC2808A-1Q1 is initially powered up from the 36V to 72V input supply. After the power supply has started, an auxiliary winding on the main power transformer provides the bias supply.

Isolation is provided by an optocoupler with regulation accomplised on the secondary side using the TL431 precision programmable reference. The internal error amplifier of the UCC2808A-1Q1 is set up as a unity gain amplifier and the compensation network is provided on the secondary side.

Many choices exist for the output inductor depending on cost and size constraints. Design options are powdered iron, molypermalloy, or the ferrite core option that is used in this design. The power transformer is a low profile design, EFD25 size, using the Magnetics Inc. P material. This material is a good choice for low power loss at high switching frequency.

The switching frequency is set at 210kHz with the RC network on the RC pin.