JAJSHD4A may   2019  – july 2023 LM5108

PRODUCTION DATA  

  1.   1
  2. 1 特長
  3. 2 アプリケーション
  4. 3 概要
  5. 4 Revision History
  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 Electrical Characteristics
    6. 6.6 Switching Characteristics
    7. 6.7 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Enable
      2. 7.3.2 Start-up and UVLO
      3. 7.3.3 Input Stages and Interlock Protection
      4. 7.3.4 Level Shifter
      5. 7.3.5 Output Stage
      6. 7.3.6 Negative Voltage Transients
    4. 7.4 Device Functional Modes
  9. 8 Application 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. 8.2.2.1 Select Bootstrap and VDD Capacitor
        2. 8.2.2.2 Estimate Driver Power Losses
        3. 8.2.2.3 Selecting External Gate Resistor
        4. 8.2.2.4 Delays and Pulse Width
        5. 8.2.2.5 External Bootstrap Diode
        6. 8.2.2.6 VDD and Input Filter
        7. 8.2.2.7 Transient Protection
      3. 8.2.3 Application Curves
  10. 9 Power Supply Recommendations
  11. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  12. 11Device and Documentation Support
    1. 11.1 サード・パーティ製品に関する免責事項
    2. 11.2 ドキュメントの更新通知を受け取る方法
    3. 11.3 サポート・リソース
    4. 11.4 Trademarks
    5. 11.5 静電気放電に関する注意事項
    6. 11.6 用語集
  13. 12Mechanical, 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

8.2.2.5 External Bootstrap Diode

The LM5108 incorporates the bootstrap diode necessary to generate the high-side bias for HO to work satisfactorily. The characteristics of this diode are important to achieve efficient, reliable operation. The characteristics to consider are forward voltage drop and dynamic resistance. Generally, low forward voltage drop diodes are preferred for low power loss during charging of the bootstrap capacitor. The device has a boot diode forward voltage drop rated at 0.9 V and dynamic resistance of 2 Ω for reliable charge transfer to the bootstrap capacitor. The dynamic characteristics to consider are diode recovery time and stored charge. Diode recovery times that are specified without operating conditions, can be misleading. Diode recovery times at no forward current (IF) can be noticeably less than with forward current applied. The LM5108 boot diode recovery is specified as 20 ns at IF = 20 mA, IREV = 0.5 A. Dynamic impedance of LM5108 bootstrap diode helps limit the peak forward current.

In applications where switching frequencies are very high, for example in excess of 1 MHz, and the low-side minimum pulse widths are very small, the diode peak forward current could be very high and peak reverse current could also be very high, specifically if high bootstrap capacitor value has been chosen. In such applications it might be advisable to use external Schottky diode as bootstrap diode. It is safe to at least make a provision for such diode on the board if possible.