ZHCS530I September   2007  – January 2018 LM3102

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      典型应用原理图
      2.      效率与负载电流间的关系 (VOUT = 3.3V)
  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
    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  COT Control Circuit Overview
      2. 7.3.2  Start-Up Regulator (VCC)
      3. 7.3.3  Regulation Comparator
      4. 7.3.4  Zero Coil Current Detect
      5. 7.3.5  Overvoltage Comparator
      6. 7.3.6  Current Limit
      7. 7.3.7  N-Channel MOSFET and Driver
      8. 7.3.8  Soft-Start
      9. 7.3.9  Thermal Protection
      10. 7.3.10 Thermal Derating
    4. 7.4 Device Functional Modes
      1. 7.4.1 ON-Time Timer, Shutdown
  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 Design Steps for the LM3102 Application
        2. 8.2.2.2 External Components
      3. 8.2.3 Application Curve
    3. 8.3 System Examples
  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 社区资源
    2. 11.2 商标
    3. 11.3 静电放电警告
    4. 11.4 术语表
  12. 12机械、封装和可订购信息

封装选项

请参考 PDF 数据表获取器件具体的封装图。

机械数据 (封装 | 引脚)
  • YPA|28
  • PWP|20
散热焊盘机械数据 (封装 | 引脚)
订购信息

7.3.6 Current Limit

Current limit detection is carried out during the OFF-time by monitoring the re-circulating current through the synchronous MOSFET. Referring to the Functional Block Diagram, when the main MOSFET is turned off, the inductor current flows through the load, the PGND pin and the internal synchronous MOSFET. If this current exceeds 2.7 A, the current limit comparator toggles, and as a result disabling the start of the next ON-time period. The next switching cycle starts when the re-circulating current falls back below 2.7 A (and the voltage at the FB pin is below 0.8V). The inductor current is monitored during the ON-time of the synchronous MOSFET. As long as the inductor current exceeds 2.7 A, the main MOSFET will remain inhibited to achieve current limit. The operating frequency is lower during current limit due to a longer OFF-time.

Figure 20 illustrates an inductor current waveform. On average, the output current IOUT is the same as the inductor current IL, which is the average of the rippled inductor current. In case of current limit (the current limit portion of Figure 20), the next ON-time will not initiate until that the current drops below 2.7 A (assume the voltage at the FB pin is lower than 0.8 V). During each ON-time the current ramps up an amount equal to:

Equation 4. LM3102 30021338.gif

During current limit, the LM3102 operates in a constant current mode with an average output current IOUT(CL) equal to 2.7 A + ILR / 2.

LM3102 30021326.pngFigure 20. Inductor Current - Current Limit Operation