JAJSGD0I April   2004  – October 2018 LM5008

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回路とブロック図
  4. 4 改訂履歴
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 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
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Hysteretic Control Circuit Overview
      2. 7.3.2 High Voltage Start-Up Regulator
      3. 7.3.3 Regulation Comparator
      4. 7.3.4 Overvoltage Comparator
      5. 7.3.5 On-Time Generator and Shutdown
      6. 7.3.6 Current Limit
      7. 7.3.7 N-Channel Buck Switch and Driver
      8. 7.3.8 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Active Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Minimum Load Current
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Custom Design With WEBENCH® Tools
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
  11. 11デバイスおよびドキュメントのサポート
    1. 11.1 デバイス・サポート
      1. 11.1.1 デベロッパー・ネットワークの製品に関する免責事項
      2. 11.1.2 WEBENCH®ツールによるカスタム設計
      3. 11.1.3 開発サポート
    2. 11.2 ドキュメントのサポート
      1. 11.2.1 関連資料
        1. 11.2.1.1 PCBレイアウトについてのリソース
        2. 11.2.1.2 熱設計についてのリソース
    3. 11.3 ドキュメントの更新通知を受け取る方法
    4. 11.4 コミュニティ・リソース
    5. 11.5 商標
    6. 11.6 静電気放電に関する注意事項
    7. 11.7 Glossary
  12. 12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 Current Limit

The LM5008 contains an intelligent current limit off-timer. If the current in the buck switch exceeds 0.5 A the present cycle is immediately terminated, and a non-resetable off-timer is initiated. The length of off-time is controlled by an external resistor (RCL) and the FB voltage (see Figure 4). When FB = 0 V, a maximum off-time is required, and the time is preset to 35 µs. This condition occurs when the output is shorted, and during the initial part of start-up. This amount of time ensures safe short-circuit operation up to the maximum input voltage of 95 V. In cases of overload where the FB voltage is above zero volts (not a short circuit), the current limit off-time will be less than 35 µs. Reducing the off-time during less severe overloads reduces the amount of foldback, recovery time, and the start-up time. The off-time is calculated from Equation 5.

Equation 5. LM5008 20097928.gif

The current limit sensing circuit is blanked for the first 50-70 ns of each on-time so it is not falsely tripped by the current surge which occurs at turnon. The current surge is required by the re-circulating diode (D1) for its turnoff recovery.