ZHCS531G September   2007  – January 2018 LM3103

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     典型应用原理图
  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 Functional Block Diagram
    2. 7.2 Feature Description
      1. 7.2.1  COT Control Circuit Overview
      2. 7.2.2  Startup Regulator (VCC)
      3. 7.2.3  Regulation Comparator
      4. 7.2.4  Zero Coil Current Detect
      5. 7.2.5  Over-Voltage Comparator
      6. 7.2.6  ON-Time Timer, Shutdown
      7. 7.2.7  Current Limit
      8. 7.2.8  N-Channel MOSFET and Driver
      9. 7.2.9  Soft-Start
      10. 7.2.10 Thermal Protection
  8. 8 Applications and Implementation
    1. 8.1 Application Information
      1. 8.1.1 External Components
  9. 9 器件和文档支持
    1. 9.1 接收文档更新通知
    2. 9.2 社区资源
    3. 9.3 商标
    4. 9.4 静电放电警告
    5. 9.5 Glossary
  10. 10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

7.2.6 ON-Time Timer, Shutdown

The on-time of the LM3103 main MOSFET is determined by the resistor RON and the input voltage VIN. It is calculated as follows:

Equation 4. LM3103 30029724.gif

The inverse relationship of ton and VIN gives a nearly constant frequency as VIN is varied. RON should be selected such that the on-time at maximum VIN is greater than 100 ns. The on-timer has a limiter to ensure a minimum of 100 ns for ton. This limits the maximum operating frequency, which is governed by the following equation:

Equation 5. LM3103 30029725.gif

The LM3103 can be remotely shut down by pulling the voltage of the EN pin below 1.6 V. In this shutdown mode, the SS pin is internally grounded, the on-timer is disabled, and bias currents are reduced. Releasing the EN pin allows normal operation to resume because the EN pin is internally pulled up.

LM3103 30029726.pngFigure 19. Shutdown Implementation