ZHCSI45 April   2018 LM3478Q-Q1

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      典型的高效升压转换器
  4. 4 修订历史记录
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings - LM3478Q-Q1
    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 Overvoltage Protection
      2. 7.3.2 Slope Compensation Ramp
      3. 7.3.3 Frequency Adjust/Shutdown
      4. 7.3.4 Short-Circuit Protection
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Typical High Efficiency Step-Up (Boost) Converter
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1  Custom Design with WEBENCH Tools
          2. 8.2.1.2.2  Power Inductor Selection
          3. 8.2.1.2.3  Programming the Output Voltage
          4. 8.2.1.2.4  Setting the Current Limit
          5. 8.2.1.2.5  Current Limit with External Slope Compensation
          6. 8.2.1.2.6  Power Diode Selection
          7. 8.2.1.2.7  Power MOSFET Selection
          8. 8.2.1.2.8  Input Capacitor Selection
          9. 8.2.1.2.9  Output Capacitor Selection
          10. 8.2.1.2.10 Compensation
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Typical SEPIC Converter
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Power MOSFET Selection
          2. 8.2.2.2.2 Power Diode Selection
          3. 8.2.2.2.3 Selection of Inductors L1 and L2
          4. 8.2.2.2.4 Sense Resistor Selection
          5. 8.2.2.2.5 Sepic Capacitor Selection
          6. 8.2.2.2.6 Input Capacitor Selection
          7. 8.2.2.2.7 Output Capacitor Selection
        3. 8.2.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11器件和文档支持
    1. 11.1 使用 WEBENCH 工具创建定制设计
    2. 11.2 接收文档更新通知
    3. 11.3 文档支持
      1. 11.3.1 相关文档
    4. 11.4 商标
    5. 11.5 静电放电警告
    6. 11.6 术语表
  12. 12机械、封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

8.2.1 Typical High Efficiency Step-Up (Boost) Converter

LM3478Q-Q1 10135501Q1.gifFigure 27. Typical High Efficiency Step-Up (Boost) Converter Schematic

The boost converter converts a low input voltage into a higher output voltage. The basic configuration for a boost converter is shown in Figure 28. In the CCM (when the inductor current never reaches zero at steady state), the boost regulator operates in two states. In the first state of operation, MOSFET Q is turned on and energy is stored in the inductor. During this state, diode D is reverse biased and load current is supplied by the output capacitor, COUT.

In the second state, MOSFET Q is off and the diode is forward biased. The energy stored in the inductor is transferred to the load and the output capacitor. The ratio of the switch on time to the total period is the duty cycle D as shown in Equation 8.

Equation 8. D = 1 - (Vin / Vout)

Including the voltage drop across the MOSFET and the diode the definition for the duty cycle is shown in Equation 9.

Equation 9. D = 1 - ((Vin - Vq)/(Vout + Vd))

Vd is the forward voltage drop of the diode and Vq is the voltage drop across the MOSFET when it is on.

LM3478Q-Q1 10135522.png
a. First Cycle Operation
b. Second Cycle of Operation
Figure 28. Simplified Boost Converter
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