JAJSHL7F October   2011  – June 2019 LMR24220

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      代表的なアプリケーション
  4. 4 改訂履歴
  5. 5 Pin Configuration and Functions
    1.     Pin Descriptions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Recommended Operating Ratings
    3. 6.3 Electrical Characteristics
    4. 6.4 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  CoT Control Circuit Overview
      2. 7.3.2  Start-up Regulator (VCC)
      3. 7.3.3  Regulation Comparator
      4. 7.3.4  Zero Coil Current Detect
      5. 7.3.5  Overvoltage Comparator
      6. 7.3.6  On-Time Timer, Shutdown
      7. 7.3.7  Current Limit
      8. 7.3.8  N-Channel MOSFET and Driver
      9. 7.3.9  Soft Start
      10. 7.3.10 Thermal Protection
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Detailed Design Procedure
        1. 8.2.1.1 Custom Design With WEBENCH® Tools
        2. 8.2.1.2 External Components
      2. 8.2.2 Application Curve
  9. 9 Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Package Considerations
    3. 9.3 Thermal Derating
  10. 10デバイスおよびドキュメントのサポート
    1. 10.1 デバイス・サポート
      1. 10.1.1 開発サポート
        1. 10.1.1.1 WEBENCH®ツールによるカスタム設計
    2. 10.2 ドキュメントの更新通知を受け取る方法
    3. 10.3 コミュニティ・リソース
    4. 10.4 商標
    5. 10.5 静電気放電に関する注意事項
    6. 10.6 Glossary
  11. 11メカニカル、パッケージ、および注文情報

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

7.3.6 On-Time Timer, Shutdown

The on-time of the LMR24220 main MOSFET is determined by the resistor RON and the input voltage VIN. It is calculated as follows:

Equation 4. LMR24220 30167623.gif

The inverse relationship of ton and VIN gives a nearly constant frequency as VIN is varied. Select RON so that the on-time at maximum VIN is greater than 150 ns. The on-timer has a limiter to ensure a minimum of 150 ns for ton. This limits the maximum operating frequency, which is governed by Equation 5:

Equation 5. LMR24220 30167624.gif

The LMR24220 can be remotely shutdown by pulling the voltage of the EN pin below 1 V. In this shutdown mode, the SS pin is internally grounded, the on-timer is disabled, and bias currents are reduced. Releasing the EN pin allows normal operation to resume because the EN pin is internally pulled up.

LMR24220 30167625.pngFigure 17. Shutdown Implementation