JAJSBG5H September   2003  – November 2018 LM5007

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の回路図
  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 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 Bias Supply Regulator
      3. 7.3.3 Overvoltage Comparator
      4. 7.3.4 On-Time Generator and Shutdown
      5. 7.3.5 Overcurrent Protection
      6. 7.3.6 N-Channel Buck Switch and Driver
      7. 7.3.7 Thermal Protection
      8. 7.3.8 Minimum Load Current
      9. 7.3.9 Ripple Configuration
    4. 7.4 Device Functional Modes
      1. 7.4.1 Standby Mode with VIN
      2. 7.4.2 Shutdown Mode
  8. 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 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Custom Design With Excel Quickstart Tool
        3. 8.2.2.3 Feedback Resistors, RFB1 and RFB2
        4. 8.2.2.4 Switching Frequency Selection, RON
        5. 8.2.2.5 Buck Inductor, L1
        6. 8.2.2.6 Output Capacitor, COUT
        7. 8.2.2.7 Type I Ripple Circuit, RC
        8. 8.2.2.8 Input Capacitor, CIN
        9. 8.2.2.9 Current Limit, RCL
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  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 コミュニティ・リソース
    4. 11.4 商標
    5. 11.5 静電気放電に関する注意事項
    6. 11.6 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

7.3.5 Overcurrent Protection

The LM5007 contains an intelligent current limit off-timer intended to reduce the foldback characteristic inherent with fixed off-time overcurrent protection (OCP) schemes. If the current in the buck switch exceeds 725 mA, the present cycle on-time is immediately terminated (cycle-by-cycle current limit). Following the termination of the cycle a non-resettable current limit off-timer is initiated. The duration of the off-time is a function of the external resistor (RCL) and the FB voltage. When the FB voltage equals zero, the current limit off-time is internally preset to 17 µs. This condition occurs during a short-circuit condition when a maximum amount of off-time is required.

In case of output overload (not a complete short circuit), the current limit off-time is reduced as a function of the output voltage (measured at the FB pin). Scaling the off-time with smaller overloads reduces the amount of foldback and also reduces the initial start-up time. Calculate the current limit off-time for a given FB voltage and RCL resistor using Equation 5.

Equation 5. LM5007 q_toff-CL_nvs252.gif

Select the current limit off-time such that it is less than the MOSFET off-time during normal steady-state switching operation. Applications utilizing low-resistance inductors and/or a low-voltage-drop freewheeling power diodes may require special evaluation at high line, short-circuited conditions. In this special case the preset 17-µs off-time (VFB = 0 V) may be insufficient to provide inductor volt-seconds balance. Additional inductor resistance, output resistance or a larger voltage drop diode may be necessary to balance inductor volt-seconds and limit the short-circuit current.