SLUSCJ9E June   2016  – December 2021 UCC21520

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Description (continued)
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information
    5. 7.5  Power Ratings
    6. 7.6  Insulation Specifications
    7. 7.7  Safety-Related Certifications
    8. 7.8  Safety-Limiting Values
    9. 7.9  Electrical Characteristics
    10. 7.10 Switching Characteristics
    11. 7.11 Insulation Characteristics Curves
    12. 7.12 Typical Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Propagation Delay and Pulse Width Distortion
    2. 8.2 Rising and Falling Time
    3. 8.3 Input and Disable Response Time
    4. 8.4 Programable Dead Time
    5. 8.5 Power-up UVLO Delay to OUTPUT
    6. 8.6 CMTI Testing
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 VDD, VCCI, and Undervoltage Lock Out (UVLO)
      2. 9.3.2 Input and Output Logic Table
      3. 9.3.3 Input Stage
      4. 9.3.4 Output Stage
      5. 9.3.5 Diode Structure in the UCC21520 and the UCC21520A
    4. 9.4 Device Functional Modes
      1. 9.4.1 Disable Pin
      2. 9.4.2 Programmable Dead-Time (DT) Pin
        1. 9.4.2.1 Tying the DT Pin to VCC
        2. 9.4.2.2 DT Pin Connected to a Programming Resistor between DT and GND Pins
        3. 9.4.2.3 41
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Designing INA/INB Input Filter
        2. 10.2.2.2 Select External Bootstrap Diode and its Series Resistor
        3. 10.2.2.3 Gate Driver Output Resistor
        4. 10.2.2.4 Gate to Source Resistor Selection
        5. 10.2.2.5 Estimate Gate Driver Power Loss
        6. 10.2.2.6 Estimating Junction Temperature
        7. 10.2.2.7 Selecting VCCI, VDDA/B Capacitor
          1. 10.2.2.7.1 Selecting a VCCI Capacitor
          2. 10.2.2.7.2 Selecting a VDDA (Bootstrap) Capacitor
          3. 10.2.2.7.3 Select a VDDB Capacitor
        8. 10.2.2.8 Dead Time Setting Guidelines
        9. 10.2.2.9 Application Circuits with Output Stage Negative Bias
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
  13. 13Device and Documentation Support
    1. 13.1 Third-Party Products Disclaimer
    2. 13.2 Documentation Support
      1. 13.2.1 Related Documentation
    3. 13.3 Certifications
    4. 13.4 Receiving Notification of Documentation Updates
    5. 13.5 Support Resources
    6. 13.6 Trademarks
    7. 13.7 Electrostatic Discharge Caution
    8. 13.8 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

10.2.2.8 Dead Time Setting Guidelines

For power converter topologies utilizing half-bridges, the dead time setting between the top and bottom transistor is important for preventing shoot-through during dynamic switching.

The UCC21520 dead time specification in the electrical table is defined as the time interval from 90% of one channel’s falling edge to 10% of the other channel’s rising edge (see Figure 8-4). This definition ensures that the dead time setting is independent of the load condition, and guarantees linearity through manufacture testing. However, this dead time setting may not reflect the dead time in the power converter system, since the dead time setting is dependent on the external gate drive turn-on/off resistor, DC-Link switching voltage/current, as well as the input capacitance of the load transistor.

Here is a suggestion on how to select an appropriate dead time for UCC21520:

Equation 22. GUID-0E3B9957-9F98-48A3-821D-22FC0DF9B456-low.gif

where

  • DTsetting: UCC21520 dead time setting in ns, DTSetting = 10 × RDT(in kΩ).
  • DTReq: System required dead time between the real VGS signal of the top and bottom switch with enough margin, or ZVS requirement.
  • TF_Sys: In-system gate turn-off falling time at worst case of load, voltage/current conditions.
  • TR_Sys: In-system gate turn-on rising time at worst case of load, voltage/current conditions.
  • TD(on): Turn-on delay time, from 10% of the transistor gate signal to power transistor gate threshold.

In the example, DTSetting is set to 250 ns.

It should be noted that the UCC21520 dead time setting is decided by the DT pin configuration (See Section 9.4.2), and it cannot automatically fine-tune the dead time based on system conditions. It is recommended to parallel a ceramic capacitor, 2.2 nF or above, close to the DT pin with RDT to achieve better noise immunity.