SLUSCK0G November   2017  – November 2024 UCC21220 , UCC21220A

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  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  Power Ratings
    6. 6.6  Insulation Specifications
    7. 6.7  Safety-Limiting Values
    8. 6.8  Electrical Characteristics
    9. 6.9  Switching Characteristics
    10. 6.10 Thermal Derating Curves
    11. 6.11 Typical Characteristics
  8. 7 Parameter Measurement Information
    1. 7.1 Minimum Pulses
    2. 7.2 Propagation Delay and Pulse Width Distortion
    3. 7.3 Rising and Falling Time
    4. 7.4 Input and Disable Response Time
    5. 7.5 Power-up UVLO Delay to OUTPUT
    6. 7.6 CMTI Testing
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 VDD, VCCI, and Under Voltage Lock Out (UVLO)
      2. 8.3.2 Input and Output Logic Table
      3. 8.3.3 Input Stage
      4. 8.3.4 Output Stage
      5. 8.3.5 Diode Structure in UCC21220 and UCC21220A
    4. 8.4 Device Functional Modes
      1. 8.4.1 Disable Pin
  10. 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 Designing INA/INB Input Filter
        2. 9.2.2.2 Select External Bootstrap Diode and its Series Resistor
        3. 9.2.2.3 Gate Driver Output Resistor
        4. 9.2.2.4 Estimating Gate Driver Power Loss
        5. 9.2.2.5 Estimating Junction Temperature
        6. 9.2.2.6 Selecting VCCI, VDDA/B Capacitor
          1. 9.2.2.6.1 Selecting a VCCI Capacitor
          2. 9.2.2.6.2 Selecting a VDDA (Bootstrap) Capacitor
          3. 9.2.2.6.3 Select a VDDB Capacitor
        7. 9.2.2.7 Application Circuits with Output Stage Negative Bias
      3. 9.2.3 Application Curves
  11. 10Power Supply Recommendations
  12. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Component Placement Considerations
      2. 11.1.2 Grounding Considerations
      3. 11.1.3 High-Voltage Considerations
      4. 11.1.4 Thermal Considerations
    2. 11.2 Layout Example
  13. 12Device and Documentation Support
    1. 12.1 Third-Party Products Disclaimer
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 Receiving Notification of Documentation Updates
    4. 12.4 Support Resources
    5. 12.5 Trademarks
    6. 12.6 Electrostatic Discharge Caution
    7. 12.7 Glossary
  14. 13Revision History
  15. 14Mechanical, Packaging, and Orderable Information

9.2.2.3 Gate Driver Output Resistor

The external gate driver resistors, RON/ROFF, are used to:

  1. Limit ringing caused by parasitic inductances/capacitances.
  2. Limit ringing caused by high voltage/current switching dv/dt, di/dt, and body-diode reverse recovery.
  3. Fine-tune gate drive strength, i.e. peak sink and source current to optimize the switching loss.
  4. Reduce electromagnetic interference (EMI).

As mentioned in Section 8.3.4, the UCC21220 and UCC21220A have a pull-up structure with a P-channel MOSFET and an additional pull-up N-channel MOSFET in parallel. The combined peak source current is 4 A. Therefore, the peak source current can be predicted with Equation 2 and Equation 3:

Equation 2. UCC21220 UCC21220A
Equation 3. UCC21220 UCC21220A

where

  • RON: External turn-on resistance.
  • RGFET_INT: Power transistor internal gate resistance, found in the power transistor datasheet.
  • IO+ = Peak source current – The minimum value between 4 A, the gate driver peak source current, and the calculated value based on the gate drive loop resistance.

In this example:

Equation 4. UCC21220 UCC21220A
Equation 5. UCC21220 UCC21220A

Therefore, the high-side and low-side peak source current is 2.3 A and 2.5 A respectively. Similarly, the peak sink current can be calculated with Equation 6 and Equation 7:

Equation 6. UCC21220 UCC21220A
Equation 7. UCC21220 UCC21220A

where

  • ROFF: External turn-off resistance, ROFF=0 in this example;
  • VGDF: The anti-parallel diode forward voltage drop which is in series with ROFF. The diode in this example is an MSS1P4.
  • IO-: Peak sink current – the minimum value between 6 A, the gate driver peak sink current, and the calculated value based on the gate drive loop resistance.

In this example,

Equation 8. UCC21220 UCC21220A
Equation 9. UCC21220 UCC21220A

Therefore, the high-side and low-side peak sink current is 5.0 A and 5.4A respectively.

Importantly, the estimated peak current is also influenced by PCB layout and load capacitance. Parasitic inductance in the gate driver loop can slow down the peak gate drive current and introduce overshoot and undershoot. Therefore, it is strongly recommended that the gate driver loop should be minimized. On the other hand, the peak source/sink current is dominated by loop parasitics when the load capacitance (CISS) of the power transistor is very small (typically less than 1 nF), because the rising and falling time is too small and close to the parasitic ringing period.