JAJS194E January   2007  – June 2019 TPS40077

PRODUCTION DATA.  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
    1.     Device Images
      1.      アプリケーション概略図
  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 Electrical Characteristics
    5. 6.5 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  Minimum Pulse Duration
      2. 7.3.2  Slew Rate Limit On VDD
      3. 7.3.3  Setting The Switching Frequency (Programming The Clock Oscillator)
      4. 7.3.4  Loop Compensation
      5. 7.3.5  Shutdown and Sequencing
      6. 7.3.6  Boost and LVBP Bypass Capacitance
      7. 7.3.7  Internal Regulators
      8. 7.3.8  Power Dissipation
      9. 7.3.9  Boost Diode
      10. 7.3.10 Synchronous Rectifier Control
    4. 7.4 Programming
      1. 7.4.1 Programming The Ramp Generator Circuit and UVLO
      2. 7.4.2 Programming Soft Start
      3. 7.4.3 Programming Short-Circuit Protection
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Buck Regulator 8-V to 16-V Input, 1.8-V Output at 10 A
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Power Train Components
            1. 8.2.1.2.1.1  Output Inductor, LOUT
            2. 8.2.1.2.1.2  Output Capacitor, COUT, ELCO and MLCC
            3. 8.2.1.2.1.3  Input Capacitor, CIN ELCO and MLCC
            4. 8.2.1.2.1.4  Switching MOSFET, QSW
            5. 8.2.1.2.1.5  Rectifier MOSFET, QSR
            6. 8.2.1.2.1.6  Timing Resistor, RT
            7. 8.2.1.2.1.7  Feed-Forward and UVLO Resistor, RKFF
            8. 8.2.1.2.1.8  Soft-Start Capacitor, CSS
            9. 8.2.1.2.1.9  Short-Circuit Protection, RILIM and CILIM
            10. 8.2.1.2.1.10 Boost Voltage, CBOOST and DBOOST (Optional)
            11. 8.2.1.2.1.11 Closing the Feedback Loop, RZ1, RP1, RPZ2, RSET1, RSET2, CZ2, CP2, and CPZ1
        3. 8.2.1.3 Application Curves
    3. 8.3 Additional System Examples
  9. 9 Layout
    1. 9.1 Layout Guidelines
  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 デベロッパー・ネットワークの製品に関する免責事項
    2. 10.2 ドキュメントのサポート
      1. 10.2.1 関連資料
    3. 10.3 ドキュメントの更新通知を受け取る方法
    4. 10.4 コミュニティ・リソース
    5. 10.5 商標
    6. 10.6 静電気放電に関する注意事項
    7. 10.7 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

8.2.1.2.1.1 Output Inductor, LOUT

The output inductor is one of the most important components to select. It stores the energy necessary to keep the output regulated when the switch FET is turned off. The value of the output inductor dictates the peak and RMS currents in the converter. These currents are important when selecting other components. Equation 18 can be used to calculate a value for LOUT for this module which operates at a switching frequency (f) of 300 kHz.

Equation 18. TPS40077 q01_lout_lus714.gif

IRIPPLE is the allowable ripple in the inductor. Select IRIPPLE to be between 20% and 30% of maximum IOUT. For this design, IRIPPLE of 2.5 A was selected. Calculated LOUT is 2.13 μH. A standard inductor with value of 2.5 μH was chosen. This will reduce IRIPPLE by about 17% to 2.07 A.

This IRIPPLE value can be used calculate the rms and peak current flowing in LOUT with Equation 19. Note that this peak current is also seen by the switching FET and synchronous rectifier.

Equation 19. TPS40077 q02_ilout_lus714.gif

The power loss from the selected inductor DCR is 357 mW. The ac core loss for this Coilcraft inductor may be found from the Coilcraft Web site, where there is a loss calculator. The loss is 179 mW calculated with Equation 20.

Equation 20. TPS40077 q03_ipk_lus714.gif

The inductor is selected with a saturation current higher than this current plus the current that is developed charging the output capacitance during the soft-start interval.