SGLS318A November   2005  – November 2015 UC2854B-EP

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Multiply/Square and Divide
      2. 8.3.2 Voltage Amplifier
      3. 8.3.3 Current Amplifier
      4. 8.3.4 Miscellaneous
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1  Switching Frequency
        2. 9.2.2.2  Inductor Selection
        3. 9.2.2.3  Output Capacitor
        4. 9.2.2.4  Switch and Diode
        5. 9.2.2.5  Current Sensing
        6. 9.2.2.6  Peak Current Limit
        7. 9.2.2.7  Multiplier Set-up
        8. 9.2.2.8  Feedforward Voltage
        9. 9.2.2.9  Multiplier Input Current
        10. 9.2.2.10 Oscillator Frequency
        11. 9.2.2.11 Current Error Amplifier Compensation
        12. 9.2.2.12 Voltage Error Amplifier Compensation
        13. 9.2.2.13 Feedforward Voltage Divider Filter Capacitors
        14. 9.2.2.14 Design Procedure Summary
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Community Resources
    2. 12.2 Trademarks
    3. 12.3 Electrostatic Discharge Caution
    4. 12.4 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

5 Description (continued)

The UC2854A/B products improve upon the UC2854 by offering a wide bandwidth, low offset current amplifier, a faster responding and improved accuracy enable comparator, a VREF GOOD comparator, UVLO threshold options (16 V/10 V for offline, 10.5 V/10 V for startup from an auxiliary 12-V regulator), lower startup supply current, and an enhanced multiply/divide circuit.

New features like the amplifier output clamps, improved amplifier current sinking capability, and low offset VAC pin reduce the external component count while improving performance. Improved common mode input range of the multiplier output/current amplifier input allow the designer greater flexibility in choosing a method for current sensing. Unlike its predecessor, RSET controls only oscillator charging current and has no effect on clamping the maximum multiplier output current. This current is now clamped to a maximum of 2 × IAC at all times which simplifies the design process and provides foldback power limiting during brownout and extreme low line conditions.