SLUSCM5A August   2017  – February 2018 UCC24612

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Flyback with High-Side SR
      2.      Flyback with Low-Side SR
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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 Timing Requirements
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Power Management
      2. 7.3.2 Synchronous Rectifier Control
      3. 7.3.3 Adaptive Blanking Time
        1. 7.3.3.1 Turn-On Blanking Timer (Minimum On Time)
        2. 7.3.3.2 Turn-Off Blanking Timer
        3. 7.3.3.3 SR Turn-on Re-arm
      4. 7.3.4 Gate Voltage Clamping
      5. 7.3.5 Standby Mode
    4. 7.4 Device Functional Modes
      1. 7.4.1 UVLO Mode
      2. 7.4.2 Standby Mode
      3. 7.4.3 Run Mode
  8. 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 SR MOSFET Selection
        2. 8.2.2.2 Bypass Capacitor Selection
        3. 8.2.2.3 Snubber design
        4. 8.2.2.4 High-Side Operation
      3. 8.2.3 Application Curves
        1. 8.2.3.1 Steady State Testing Low-Side Configuration
        2. 8.2.3.2 Steady State Testing High-Side Configuration
  9. 9 Power Supply Recommendations
  10. 10PCB Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Community Resources
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.3.3.1 Turn-On Blanking Timer (Minimum On Time)

Right after SR turn-on, for some topologies, such as Flyback, the SR starts to conduct with its maximum current. Due to the parasitic ringing, SR sensed voltage drop may trip the turn-off threshold and prematurely turn off the SR. This is largely caused by the ringing due to the package inductance of the SR MOSFET. The ringing voltage can be managed through appropriate snubbing and use of low package inductance MOSFETs. To further improve the noise immunity, UCC24612-1 blanks the turn-off comparator with a fixed 360-ns (540 ns for UCC24612-2) minimum on-time timer. The SR needs to conduct a minimum of 360 ns (540 ns for UCC24612-2) regardless of its turn-off comparator state. The minimum on-time is short enough to allow the UCC24612 to be used at up to 1 MHz switching frequency (1 MHz for UCC24612-1 and 800kHz for UCC24612-2), while still maintaining good noise immunity. Due to the different applications, the minimum on-time is set up differently for UCC24612-1 and UCC24612-2. For UCC24612-1, the minimum on-time is 360 ns and for UCC24612-2, the minimum on-time is 540 ns.