JAJSRH6E February   2010  – November 2023 UCC27321-Q1 , UCC27322-Q1

PRODUCTION DATA  

  1.   1
  2. 特長
  3. アプリケーション
  4. 概要
  5. 概要 (続き)
  6. Related Products
  7. Pin Configuration and Functions
  8. 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 Electrical Characteristics
    6. 7.6 Switching Characteristics
    7. 7.7 Typical Characteristics
  9. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Input Stage
      2. 8.3.2 Output Stage
      3. 8.3.3 Source and Sink Capabilities During Miller Plateau
      4. 8.3.4 VDD
      5. 8.3.5 Drive Current and Power Requirements
      6. 8.3.6 Enable
    4. 8.4 Device Functional Modes
  10. 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 Input-to-Output Configuration
        2. 9.2.2.2 Input Threshold Type
        3. 9.2.2.3 VDD Bias Supply Voltage
        4. 9.2.2.4 Peak Source and Sink Currents
        5. 9.2.2.5 Enable and Disable Function
        6. 9.2.2.6 Propagation Delay
      3. 9.2.3 Application Curves
  11. 10Power Supply Recommendations
    1.     40
  12. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Thermal Considerations
    4. 11.4 Power Dissipation
  13. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 サード・パーティ製品に関する免責事項
    2. 12.2 Documentation Support
      1. 12.2.1 Related Documentation
    3. 12.3 ドキュメントの更新通知を受け取る方法
    4. 12.4 サポート・リソース
    5. 12.5 Trademarks
    6. 12.6 静電気放電に関する注意事項
    7. 12.7 用語集
  14. 13Revision History
  15. 14Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ(パッケージ|ピン)
サーマルパッド・メカニカル・データ
発注情報

Power Dissipation

The UCC2732x-Q1 family of drivers are capable of delivering 9-A of current to a MOSFET gate for a period of several hundred nanoseconds. High peak current is required to turn an N-channel device ON quickly. Then, to turn the device OFF, the driver is required to sink a similar amount of current to ground. This repeats at the operating frequency of the power device. An N-channel MOSFET is used in this discussion because it is the most common type of switching device used in high-frequency power conversion equipment.

Design And Application Guide For High Speed MOSFET Gate Drive Circuits and Practical Considerations in High Performance MOSFET, IGBT and MCT Gate Drive Circuits contain detailed discussions of the drive current required to drive a power MOSFET and other capacitive-input switching devices. Much information is provided in tabular form to give a range of the current required for various devices at various frequencies. The information pertinent to calculating gate drive current requirements is summarized here.

When a driver device is tested with a discrete, capacitive load it is a fairly simple matter to calculate the power that is required from the bias supply. The energy that must be transferred from the bias supply to charge the capacitor is given by Equation 8.

Equation 8. GUID-4A53EC80-42EB-4DD6-B232-0E2CF0A3540B-low.gif

where

  • C is the load capacitor
  • V is the bias voltage feeding the driver

There is an equal amount of energy transferred to ground when the capacitor is discharged. This leads to a power loss given by Equation 9.

Equation 9. GUID-78F59020-922D-476C-B0C9-9250744A95C3-low.gif

where

  • f is the switching frequency

This power is dissipated in the resistive elements of the circuit. Thus, with no external resistor between the driver and gate, this power is dissipated inside the driver. Half of the total power is dissipated when the capacitor is charged, and the other half is dissipated when the capacitor is discharged. An example using the conditions of the previous gate-drive waveform helps to clarify this.

With VDD = 12 V, CLOAD = 10 nF, and f = 300 kHz, the power loss can be calculated as shown in Equation 11.

Equation 10. GUID-FF8075AC-BD66-4C91-A02D-C3E3D84C8521-low.gif

With a 12-V supply, this would equate, as shown in Equation 11, to a current of:

Equation 11. GUID-D940CD02-88B0-4D8F-8F1E-52745712E6E2-low.gif

The switching load presented by a power MOSFETcan be converted to an equivalent capacitance by examining the gate charge required to switch the device. This gate charge includes the effects of the input capacitance plus the added charge required to swing the drain of the device between the ON and OFF states. Most manufacturers provide specifications that provide the typical and maximum gate charge, in nC, to switch the device under specified conditions. Using the gate charge Qg, one can determine the power that must be dissipated when charging a capacitor. This is done by using the equivalence Qg = CeffV to provide Equation 12 for power.

Equation 12. GUID-1082AB6D-BDDF-4AA6-9B00-EFB852505B8B-low.gif

Equation 12 allows a power designer to calculate the bias power required to drive a specific MOSFET gate at a specific bias voltage.