JAJSHZ4A September   2019  – February 2020 LMR36520

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      効率と出力電流との関係 VOUT = 5V、400kHz
      2.      概略回路図
  4. 4 改訂履歴
  5. 5 Description
  6. 6 Device Comparison Table
  7. 7 Pin Configuration and Functions
    1.     Pin Functions
  8. 8 Specifications
    1. 8.1 Absolute Maximum Ratings
    2. 8.2 ESD Ratings
    3. 8.3 Recommended Operating Conditions
    4. 8.4 Thermal Information
    5. 8.5 Electrical Characteristics
    6. 8.6 Timing Requirements
    7. 8.7 Switching Characteristics
    8. 8.8 System Characteristics
    9. 8.9 Typical Characteristics
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Power-Good Flag Output
      2. 9.3.2 Enable and Start-up
      3. 9.3.3 Current Limit and Short Circuit
      4. 9.3.4 Undervoltage Lockout and Thermal Shutdown
    4. 9.4 Device Functional Modes
      1. 9.4.1 Auto Mode
      2. 9.4.2 Forced PWM Operation
      3. 9.4.3 Dropout
      4. 9.4.4 Minimum Switch On-Time
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Application
      1. 10.2.1 Design 1: Low Power 24-V, 2-A Buck Converter
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
          1. 10.2.1.2.1  Choosing the Switching Frequency
          2. 10.2.1.2.2  Setting the Output Voltage
          3. 10.2.1.2.3  Inductor Selection
          4. 10.2.1.2.4  Output Capacitor Selection
          5. 10.2.1.2.5  Input Capacitor Selection
          6. 10.2.1.2.6  CBOOT
          7. 10.2.1.2.7  VCC
          8. 10.2.1.2.8  CFF Selection
          9. 10.2.1.2.9  External UVLO
          10. 10.2.1.2.10 Maximum Ambient Temperature
      2. 10.2.2 Application Curves
    3. 10.3 What to Do and What Not to Do
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 Ground and Thermal Considerations
    2. 12.2 Layout Example
  13. 13デバイスおよびドキュメントのサポート
    1. 13.1 デバイス・サポート
      1. 13.1.1 開発サポート
    2. 13.2 ドキュメントのサポート
      1. 13.2.1 関連資料
    3. 13.3 ドキュメントの更新通知を受け取る方法
    4. 13.4 サポート・リソース
    5. 13.5 商標
    6. 13.6 静電気放電に関する注意事項
    7. 13.7 Glossary
  14. 14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

10.2.1.2.8 CFF Selection

In some cases, a feedforward capacitor can be used across RFBT to improve the load transient response or improve the loop-phase margin. This is especially true when values of RFBT > 100 kΩ are used. Large values of RFBT, in combination with the parasitic capacitance at the FB pin, can create a small signal pole that interferes with the loop stability. A CFF can help mitigate this effect. Equation 9 can be used to estimate the value of CFF. The value found with Equation 9 is a starting point; use lower values to determine if any advantage is gained by the using a CFF capacitor. The Optimizing Transient Response of Internally Compensated DC-DC Converters with Feed-forward Capacitor Application Report is helpful when experimenting with a feedforward capacitor.

Equation 9. LMR36520 CFF_eq3.gif