SLUSF25A September   2025  – November 2025 UCC27834 , UCC27884

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 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 Electrical Characteristics
    6. 5.6 Dynamic Electrical Characteristics
    7. 5.7 Timing Diagrams
    8. 5.8 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Input Stages and Interlock
      2. 6.3.2 Undervoltage Lockout (UVLO)
      3. 6.3.3 Level Shifter
      4. 6.3.4 Output Stage
      5. 6.3.5 Low Propagation Delays and Tightly Matched Outputs
      6. 6.3.6 HS Node dV/dt
      7. 6.3.7 Operation Under Negative HS Voltage Condition
    4. 6.4 Device Functional Modes
      1. 6.4.1 Input and Output Logic Table
      2. 6.4.2 Operation Under 100% Duty Cycle Condition
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Selecting HI and LI Low Pass Filter Components (RHI, RLI, CHI, CLI)
        2. 7.2.2.2 Selecting Bootstrap Capacitor (CBOOT)
        3. 7.2.2.3 Selecting VDD Bypass Capacitor (CVDD)
        4. 7.2.2.4 Selecting Bootstrap Resistor (RBOOT)
        5. 7.2.2.5 Selecting Gate Resistor RON/ROFF
        6. 7.2.2.6 Selecting Bootstrap Diode
        7. 7.2.2.7 Estimate the UCC278X4 Power Losses
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Third-Party Products Disclaimer
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 Receiving Notification of Documentation Updates
    4. 8.4 Support Resources
    5. 8.5 Trademarks
    6. 8.6 Electrostatic Discharge Caution
    7. 8.7 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

7.2.2.4 Selecting Bootstrap Resistor (RBOOT)

The optional resistor RBOOT is selected to limit the current in DBOOT and limit the ramp up slew rate of voltage of VHB–HS.  For this design, we selected a current limiting resistor of 2.2Ω.  The bootstrap diode current (IBOOT(pk)) was limited to roughly 6.5A.

Equation 6. R B O O T = 2.2   Ω
Equation 7. I B O O T p k =   V D D - V B O O T R B O O T =   15   V - 0.6   V 2.2   Ω   ≅ 6.5   A

The power dissipation capability of the bootstrap resistor is important. The bootstrap resistor must be able to withstand the short period of high power dissipation during the initial charging sequence of the bootstrap capacitor. This energy is equivalent to 1/2 × CBOOT × V2. This energy is dissipated during the charging time of the bootstrap capacitor (~3 × RBOOT × CBOOT). Special attention must be paid to use a larger size RBOOT when a larger value of CBOOT is chosen.