SLUSD48C July   2018  – March 2022 UCC24624

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
    1.     Pin 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 Timing Requirements
    7. 7.7 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 Power Management
      2. 8.3.2 Synchronous Rectifier Control
      3. 8.3.3 Turn-off Threshold Adjustment
      4. 8.3.4 Noise Immunity
        1. 8.3.4.1 On-Time Blanking
        2. 8.3.4.2 Off-Time Blanking
        3. 8.3.4.3 Two-Channel Interlock
        4. 8.3.4.4 SR Turn-on Re-arm
        5. 8.3.4.5 Adaptive Turn-on Delay
      5. 8.3.5 Gate Voltage Clamping
      6. 8.3.6 Standby Mode
    4. 8.4 Device Functional Modes
      1. 8.4.1 UVLO Mode
      2. 8.4.2 Standby Mode
      3. 8.4.3 Run Mode
  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 MOSFET Selection
        2. 9.2.2.2 Snubber Design
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
        1. 12.1.1.1 Custom Design With WEBENCH® Tools
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resources
    4. 12.4 Trademarks

8.3.4.2 Off-Time Blanking

When the converter operates in burst mode, during the off period of the secondary side synchronous rectifiers, there is large parasitic ringing (DCM ring) caused by the transformer magnetizing inductance and the switch node capacitance. During the first few ringing cycles of the off period, there is a good chance that the SR MOSFET drain voltage will resonate below the SR controller turn-on threshold. The SR MOSFET could be falsely turned on at these instances, which could introduce extra power loss and EMI noise.

In UCC24624, a fixed 650-ns off-time blanking period is implemented. After the SR is turned off, and after its drain voltage rises above 1.5 V, the SR won't turn on again for at least the off-time blanking time, regardless of its drain to source voltage. Additional adaptive turn-on delay is also implemented to further enhance the noise immunity capability during burst mode operation.