JAJSA30G November   2002  – May 2019 LM2733

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
      2.      効率と負荷電流との関係
  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 Switching Frequency
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Pin Operation
  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  Selecting the External Capacitors
        2. 8.2.2.2  Selecting the Output Capacitor
        3. 8.2.2.3  Selecting the Input Capacitor
        4. 8.2.2.4  Feedforward Compensation
        5. 8.2.2.5  Selecting Diodes
        6. 8.2.2.6  Setting the Output Voltage
        7. 8.2.2.7  Switching Frequency
        8. 8.2.2.8  Duty Cycle
        9. 8.2.2.9  Inductance Value
        10. 8.2.2.10 Maximum Switch Current
        11. 8.2.2.11 Calculating Load Current
        12. 8.2.2.12 Design Parameters VSW and ISW
        13. 8.2.2.13 Thermal Considerations
        14. 8.2.2.14 Minimum Inductance
        15. 8.2.2.15 Inductor Suppliers
      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 商標
    2. 11.2 静電気放電に関する注意事項
    3. 11.3 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

8.2.2.11 Calculating Load Current

As shown in the figure which depicts inductor current, the load current is related to the average inductor current by the relation:

Equation 7. ILOAD = IIND(AVG) x (1 - DC)

Where "DC" is the duty cycle of the application. The switch current can be found by:

Equation 8. ISW = IIND(AVG) + ½ (IRIPPLE)

Inductor ripple current is dependent on inductance, duty cycle, input voltage and frequency:

Equation 9. IRIPPLE = DC x (VIN-VSW) / (f x L)

combining all terms, we can develop an expression which allows the maximum available load current to be calculated:

Equation 10. LM2733 20055421.gif

The equation shown to calculate maximum load current takes into account the losses in the inductor or turn-OFF switching losses of the FET and diode. For actual load current in typical applications, we took bench data for various input and output voltages for both the "X" and "Y" versions of the LM2733 device and displayed the maximum load current available for a typical device in graph form:

LM2733 20055434.pngFigure 28. Max. Load Current vs VIN - "X"
LM2733 20055433.pngFigure 29. Max. Load Current vs VIN - "Y"