SLUSFG5 November   2024 UCC33421-Q1

ADVANCE INFORMATION  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison
  6. 5 Pin Configuration 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 Insulation Specifications
    6. 6.6 Safety-Related Certifications
    7. 6.7 Electrical Characteristics
    8. 6.8 External BOM Components
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Enable and Disable
      2. 7.3.2 Output Voltage Soft-Start
      3. 7.3.3 Output Voltage Steady-State Regulation
      4. 7.3.4 Protection Features
        1. 7.3.4.1 Input Under-voltage and Over-Voltage Lockout
        2. 7.3.4.2 Output Under-Voltage Protection
        3. 7.3.4.3 Output Over-Voltage Protection
        4. 7.3.4.4 Over-Temperature Protection
        5. 7.3.4.5 Fault Reporting and Auto-Restart
      5. 7.3.5 VCC Load Recommended Operating Area
      6. 7.3.6 Electromagnetic Compatibility (EMC) Considerations
    4. 7.4 Device Functional Modes
  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. 8.3 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 Device Support
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 Receiving Notification of Documentation Updates
    4. 9.4 Support Resources
    5. 9.5 Trademarks
    6. 9.6 Electrostatic Discharge Caution
    7. 9.7 Glossary
  11. 10Revision History
  12. 11Mechanical and Packaging Information

7.3.4.5 Fault Reporting and Auto-Restart

The UCC33421-Q1 has a fault reporting mechanism that can alert a system level MCU or monitoring circuitry of faulty onditions on the device that resulted in a shutdown. If an input over-voltage , over-temperature or output under voltage protection faults occur. The primary-side controller and fault monitoring system will enable a current source that will sink IFault current for tFault duration. If a resistor >18kΩ is connected between the MCU and the EN/FLT pin, the VFLT will be pulled low for the same tFault duration whenever one of the abovementioned faults occur that resulted in a shutdown of the device as shown in Figure 7-5. If the fault reporting mechanism is not required on the system, the EN/FLT pin can be connected directly to the enable source voltage without the 18kΩ resistor.

The device has a auto-restart feature that occur after the device is shutdown only due to when output under-voltage or over-temperature faults occur. After the tFault time expires, a 160ms timer will start and the part will attemp a new soft-start sequence as shown in Figure 7-6. If the fault has been removed, the VCC will soft-start to regulation successfully. If the fault remains , the part will shutdown again and report the fault. The device can continuously operate safely in hiccup mode as long as the fault occurs.

UCC33421-Q1 Fault Reporting Mechanism Figure 7-5 Fault Reporting Mechanism
UCC33421-Q1 Auto-restart operation Figure 7-6 Auto-restart operation