SLUSD12A October   2017  – February 2018 UCC28780

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
      2.      45-W, 20-V GaN-ACF Adapter Efficiency
  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 of SOIC
    5. 6.5 Thermal Information of WQFN
    6. 6.6 Electrical Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Detailed Pin Description
      1. 7.3.1 BUR Pin (Programmable Burst Mode)
      2. 7.3.2 FB Pin (Feedback Pin)
      3. 7.3.3 VDD Pin (Device Bias Supply)
      4. 7.3.4 REF Pin (Internal 5-V Bias)
      5. 7.3.5 HVG and SWS Pins
      6. 7.3.6 RTZ Pin (Sets Delay for Transition Time to Zero)
      7. 7.3.7 RDM Pin (Sets Synthesized Demagnetization Time for ZVS Tuning)
      8. 7.3.8 RUN Pin (Driver Enable Pin)
      9. 7.3.9 SET Pin
    4. 7.4 Device Functional Modes
      1. 7.4.1  Adaptive ZVS Control with Auto-Tuning
      2. 7.4.2  Dead-Time Optimization
      3. 7.4.3  Control Law across Entire Load Range
      4. 7.4.4  Adaptive Amplitude Modulation (AAM)
      5. 7.4.5  Adaptive Burst Mode (ABM)
      6. 7.4.6  Low Power Mode (LPM)
      7. 7.4.7  Standby Power Mode (SBP)
      8. 7.4.8  Startup Sequence
      9. 7.4.9  Survival Mode of VDD
      10. 7.4.10 System Fault Protections
        1. 7.4.10.1 Brown-In and Brown-Out
        2. 7.4.10.2 Output Over-Voltage Protection
        3. 7.4.10.3 Over-Temperature Protection
        4. 7.4.10.4 Programmable Over-Power Protection
        5. 7.4.10.5 Peak Current Limit
        6. 7.4.10.6 Output Short-Circuit Protection
        7. 7.4.10.7 Over-Current Protection
        8. 7.4.10.8 Thermal Shutdown
      11. 7.4.11 Pin Open/Short Protections
        1. 7.4.11.1 Protections on CS pin Fault
        2. 7.4.11.2 Protections on HVG pin Fault
        3. 7.4.11.3 Protections on RDM and RTZ pin Faults
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application Circuit
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Input Bulk Capacitance and Minimum Bulk Voltage
        2. 8.2.2.2 Transformer Calculations
          1. 8.2.2.2.1 Primary-to-Secondary Turns Ratio (NPS)
          2. 8.2.2.2.2 Primary Magnetizing Inductance (LM)
          3. 8.2.2.2.3 Primary Turns (NP)
          4. 8.2.2.2.4 Secondary Turns (NS)
          5. 8.2.2.2.5 Turns of Auxiliary Winding (NA)
          6. 8.2.2.2.6 Winding and Magnetic Core Materials
        3. 8.2.2.3 Clamp Capacitor Calculation
        4. 8.2.2.4 Bleed-Resistor Calculation
        5. 8.2.2.5 Output Filter Calculation
        6. 8.2.2.6 Calculation of ZVS Sensing Network
        7. 8.2.2.7 Calculation of Compensation Network
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 General Considerations
      2. 10.1.2 RDM and RTZ Pins
      3. 10.1.3 SWS Pin
      4. 10.1.4 VS Pin
      5. 10.1.5 BUR Pin
      6. 10.1.6 FB Pin
      7. 10.1.7 CS Pin
      8. 10.1.8 GND Pin
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.4.10.3 Over-Temperature Protection

The UCC28780 uses an external NTC resistor (RNTC) tied to the NTC pin to program a thermal shutdown temperature near the hotspot of the converter. The NTC shutdown threshold (VNTCTH) of 1 V with an internal 105-μA current source flowing through RNTC results in a 9.5-kΩ thermistor shutdown threshold. If the NTC resistance stays lower than 9.5 kΩ for more than three consecutive PWML pulses, an OTP fault event is triggered, and the 1-V threshold is increased to 2.25 V. The NTC resistance has to increase above 21.7 kΩ to reset the OTP fault. This threshold change provides a safe temperature hysteresis to help the hot-spot temperature cool down before the next VO restart attempt, reducing the thermal stress to the components. This pin can also be used as an electrical shutdown function by shorting this pin with a controlled switch to GND. With the pin shorted to GND, VVDD performs UVLO cycling, and there is at least three consecutive PWML pulses generated to check the state. The NTC pin can be left floating or tied to the REF pin if not used.

UCC28780 Timing-OTP-NTC.gifFigure 33. Timing Diagram of OTP with NTC