ZHCS785H February   2012  – May 2019 SN6501

PRODUCTION DATA.  

  1. 特性
  2. 应用
  3. 说明
    1.     Device Images
      1.      简化原理图
      2.      输出电压和效率与输出电流间的关系
  4. 修订历史记录
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 Handling Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Switching Characteristics
    7. 6.7 Typical Characteristics
  7. Parameter Measurement Information
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Push-Pull Converter
      2. 8.3.2 Core Magnetization
    4. 8.4 Device Functional Modes
      1. 8.4.1 Start-Up Mode
      2. 8.4.2 Operating Mode
      3. 8.4.3 Off-Mode
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 SN6501 Drive Capability
        2. 9.2.2.2 LDO Selection
        3. 9.2.2.3 Diode Selection
        4. 9.2.2.4 Capacitor Selection
        5. 9.2.2.5 Transformer Selection
          1. 9.2.2.5.1 V-t Product Calculation
          2. 9.2.2.5.2 Turns Ratio Estimate
          3. 9.2.2.5.3 Recommended Transformers
      3. 9.2.3 Application Curve
      4. 9.2.4 Higher Output Voltage Designs
      5. 9.2.5 Application Circuits
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12器件和文档支持
    1. 12.1 器件支持
      1. 12.1.1 第三方产品免责声明
    2. 12.2 商标
    3. 12.3 静电放电警告
    4. 12.4 Glossary
  13. 13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

Core Magnetization

Figure 38 shows the ideal magnetizing curve for a push-pull converter with B as the magnetic flux density and H as the magnetic field strength. When Q1 conducts the magnetic flux is pushed from A to A’, and when Q2 conducts the flux is pulled back from A’ to A. The difference in flux and thus in flux density is proportional to the product of the primary voltage, VP, and the time, tON, it is applied to the primary: B ≈ VP × tON.

SN6501 core_mag_llsea0.gifFigure 38. Core Magnetization and Self-Regulation Through Positive Temperature Coefficient of RDS(on)

This volt-seconds (V-t) product is important as it determines the core magnetization during each switching cycle. If the V-t products of both phases are not identical, an imbalance in flux density swing results with an offset from the origin of the B-H curve. If balance is not restored, the offset increases with each following cycle and the transformer slowly creeps toward the saturation region.

Fortunately, due to the positive temperature coefficient of a MOSFET’s on-resistance, the output FETs of the SN6501 have a self-correcting effect on V-t imbalance. In the case of a slightly longer on-time, the prolonged current flow through a FET gradually heats the transistor which leads to an increase in RDS-on. The higher resistance then causes the drain-source voltage, VDS, to rise. Because the voltage at the primary is the difference between the constant input voltage, VIN, and the voltage drop across the MOSFET, VP = VIN – VDS, VP is gradually reduced and V-t balance restored.