SLUSDS3 March   2020 UCC21739-Q1


  1. Features
  2. Applications
  3. Description
  4. Revision History
    1.     Pin Configuration and Functions
      1. Table 1. Pin Functions
  5. Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  ESD Ratings
    3. 5.3  Recommended Operating Conditions
    4. 5.4  Thermal Information
    5. 5.5  Power Ratings
    6. 5.6  Insulation Specifications
    7. 5.7  Safety-Related Certifications
    8. 5.8  Safety Limiting Values
    9. 5.9  Electrical Characteristics
    10. 5.10 Switching Characteristics
    11. 5.11 Insulation Characteristics Curves
    12. 5.12 Typical Characteristics
  6. Parameter Measurement Information
    1. 6.1 Propagation Delay
      1. 6.1.1 Regular Turn-OFF
    2. 6.2 Input Deglitch Filter
    3. 6.3 Active Miller Clamp
      1. 6.3.1 External Active Miller Clamp
    4. 6.4 Under Voltage Lockout (UVLO)
      1. 6.4.1 VCC UVLO
      2. 6.4.2 VDD UVLO
    5. 6.5 OC (Over Current) Protection
      1. 6.5.1 OC Protection with 2-Level Turn-OFF
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Power Supply
      2. 7.3.2  Driver Stage
      3. 7.3.3  VCC and VDD Undervoltage Lockout (UVLO)
      4. 7.3.4  Active Pulldown
      5. 7.3.5  Short Circuit Clamping
      6. 7.3.6  External Active Miller Clamp
      7. 7.3.7  Overcurrent and Short Circuit Protection
      8. 7.3.8  2-Level Turn-off
      9. 7.3.9  Fault (FLT, Reset and Enable (RST/EN)
      10. 7.3.10 Isolated Analog to PWM Signal Function
    4. 7.4 Device Functional Modes
  8. Applications 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. Input filters for IN+, IN- and RST/EN
        2. PWM Interlock of IN+ and IN-
        3. FLT, RDY and RST/EN Pin Circuitry
        4. RST/EN Pin Control
        5. Turn on and turn off gate resistors
        6. External Active Miller Clamp
        7. Overcurrent and Short Circuit Protection
          1. Protection Based on Power Modules with Integrated SenseFET
          2. Protection Based on Desaturation Circuit
          3. Protection Based on Shunt Resistor in Power Loop
        8. Isolated Analog Signal Sensing
          1. Isolated Temperature Sensing
          2. Isolated DC Bus Voltage Sensing
        9. Higher Output Current Using an External Current Buffer
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    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 Resource
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information



External Active Miller Clamp

External active miller clamp feature allows the gate driver to stay at the low status when the gate voltage is detected below VCLMPTH. When the other switch of the phase leg turns on, the dV/dt can cause a current through the parasitic miller capacitance of the switch and sink in the gate driver. The sinking current causes a negative voltage drop on the turn off gate resistance, and bumps up the gate voltage to cause a false turn on. The external active miller clamp features allows flexibility of board layout and active miller clamp pulldown strength. Limited by the board layout, if the driver cannot be placed close enough to the switch, external active miller clamp MOSFET can be placed close to the switch and the MOSFET can be chosen according to the peak current needed. Caution must be exercised when the driver is place far from the power semiconductor. Since the device has high peak sink and source current, the high dI/dt in the gate loop can cause a ground bounce on the board parasitics. The ground bounce can cause a positive voltage bump on CLMPE pin during the turn off transient, and results in the external active miller clamp MOSFET to turn on shortly and add extra drive strength to the sink current. To reduce the ground bounce, a 2Ω resistance is recommended to the gate of the external active clamp MOSFET.

When the VOUTH is detected to be lower than VCLMPTH above VEE, the CLMPE pin outputs a 5V voltage with respect to VEE, the external clamp FET is in linear region and the pulldown current is determined by the peak drain current, unless the on-resistance of the external clamp FET is large.

Equation 9. UCC21739-Q1 eq-10-clmpe-current.gif


  • ID_PK is the peak drain current of the external clamp FET
  • VDS is the drain-to-source voltage of the clamp FET when the CLMPE is activated
  • RDS_ON is the on-resistance of the external clamp FET

The total delay time of the active miller clamp circuit from the gate voltage detection threshold VCLMPTH can be calculated as tDCLMPE+tCLMPER. tCLMPER depends on the parameter of the external active miller clamp MOSFET. As long as the total delay time is longer than the deadtime of high side and low side switches, the driver can effectively protect the switch from false turn on issue caused by miller effect.

UCC21739-Q1 CLMPE-DIAGRAM_general.gifFigure 52. External Active Miller Clamp Configuration