JAJSHR8G July   2008  – July 2019 LM3421 , LM3423

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      代表的な昇圧アプリケーション
  4. 4 改訂履歴
  5. 5 Device Comparison
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  Current Regulators
      2. 8.3.2  Predictive Off-Time (PRO) Control
      3. 8.3.3  Average LED Current
      4. 8.3.4  Analog Dimming
      5. 8.3.5  Current Sense and Current Limit
      6. 8.3.6  Overcurrent Protection
      7. 8.3.7  Zero Current Shutdown
      8. 8.3.8  Control Loop Compensation
      9. 8.3.9  Start-Up Regulator
      10. 8.3.10 Overvoltage Lockout (OVLO)
      11. 8.3.11 Input Undervoltage Lockout (UVLO)
        1. 8.3.11.1 UVLO Only
        2. 8.3.11.2 PWM Dimming and UVLO
      12. 8.3.12 PWM Dimming
      13. 8.3.13 LM3423 Only: DPOL, FLT, TIMR, and LRDY
  9. 9 Application and Implementation
    1. 9.1 Application Information
      1. 9.1.1 Inductor
      2. 9.1.2 LED Dynamic Resistance
      3. 9.1.3 Output Capacitor
      4. 9.1.4 Input Capacitors
      5. 9.1.5 Main MOSFET / Dimming MOSFET
      6. 9.1.6 Re-Circulating Diode
      7. 9.1.7 Boost Inrush Current
      8. 9.1.8 Switching Frequency
    2. 9.2 Typical Applications
      1. 9.2.1 Basic Topology Schematics
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1  Operating Point
          2. 9.2.1.2.2  Switching Frequency
          3. 9.2.1.2.3  Average LED Current
          4. 9.2.1.2.4  Inductor Ripple Current
          5. 9.2.1.2.5  LED Ripple Current
          6. 9.2.1.2.6  Peak Current Limit
          7. 9.2.1.2.7  Loop Compensation
          8. 9.2.1.2.8  Input Capacitance
          9. 9.2.1.2.9  N-channel FET
            1. 9.2.1.2.9.1 Boost and Buck-Boost
          10. 9.2.1.2.10 Diode
          11. 9.2.1.2.11 Output OVLO
          12. 9.2.1.2.12 Input UVLO
          13. 9.2.1.2.13 PWM Dimming Method
          14. 9.2.1.2.14 Analog Dimming Method
      2. 9.2.2 LM3421 Buck-Boost Application
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
          1. 9.2.2.2.1  Operating Point
          2. 9.2.2.2.2  Switching Frequency
          3. 9.2.2.2.3  Average LED Current
          4. 9.2.2.2.4  Inductor Ripple Current
          5. 9.2.2.2.5  Output Capacitance
          6. 9.2.2.2.6  Peak Current Limit
          7. 9.2.2.2.7  Loop Compensation
          8. 9.2.2.2.8  Input Capacitance
          9. 9.2.2.2.9  N-channel FET
          10. 9.2.2.2.10 Diode
          11. 9.2.2.2.11 Input UVLO
          12. 9.2.2.2.12 Output OVLO
        3. 9.2.2.3 Application Curve
      3. 9.2.3 LM3421 BOOST Application
        1. 9.2.3.1 Design Requirements
        2. 9.2.3.2 Detailed Design Procedure
      4. 9.2.4 LM3421 Buck-Boost Application
        1. 9.2.4.1 Design Requirements
        2. 9.2.4.2 Detailed Design Procedure
      5. 9.2.5 LM3423 Boost Application
        1. 9.2.5.1 Design Requirements
        2. 9.2.5.2 Detailed Design Procedure
      6. 9.2.6 LM3421 Buck-Boost Application
        1. 9.2.6.1 Design Requirements
        2. 9.2.6.2 Detailed Design Procedure
      7. 9.2.7 LM3423 Buck Application
        1. 9.2.7.1 Design Requirements
        2. 9.2.7.2 Detailed Design Procedure
      8. 9.2.8 LM3423 Buck-Boost Application
        1. 9.2.8.1 Design Requirements
        2. 9.2.8.2 Detailed Design Procedure
      9. 9.2.9 LM3421 SEPIC Application
        1. 9.2.9.1 Design Procedure
        2. 9.2.9.2 Detailed Design Procedure
  10. 10Power Supply Recommendations
    1. 10.1 General Recommendations
    2. 10.2 Input Supply Current Limit
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12デバイスおよびドキュメントのサポート
    1. 12.1 デバイス・サポート
      1. 12.1.1 デベロッパー・ネットワークの製品に関する免責事項
    2. 12.2 関連リンク
    3. 12.3 コミュニティ・リソース
    4. 12.4 商標
    5. 12.5 静電気放電に関する注意事項
    6. 12.6 Glossary
  13. 13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

8.3.7 Zero Current Shutdown

The LM3421 and LM3423 controllers implement zero current shutdown through the EN and RPD pins. When pulled low, the EN pin places the devices into near-zero current state, where only the leakage currents occurs at the pins (typical 0.1 µA). The applications circuits frequently have resistor dividers to set UVLO, OVLO, or other similar functions. The RPD pin is an open-drain N-channel MOSFET that is enabled only when the device is enabled. Tying the bottom of all resistor dividers to the RPD pin as shown in Figure 16 allows them to float during shutdown, thus removing their current paths and providing true application-wide zero current shutdown.

LM3421 LM3423 300673j1.gifFigure 16. Zero Current Shutdown Circuit