ZHCS530I September   2007  – January 2018 LM3102

PRODUCTION DATA.  

  1. 特性
  2. 应用
  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. 修订历史记录
  5. Pin Configuration and Functions
    1.     Pin Functions
  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. 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. 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. 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

COT Control Circuit Overview

COT control is based on a comparator and a one-shot ON-timer, with the output voltage feedback (feeding to the FB pin) compared with an internal reference of 0.8 V. If the voltage of the FB pin is below the reference, the main MOSFET is turned on for a fixed ON-time determined by a programming resistor RON and the input voltage VIN, upon which the ON-time varies inversely. Following the ON-time, the main MOSFET remains off for a minimum of 260 ns. Then, if the voltage of the FB pin is below the reference, the main MOSFET is turned on again for another ON-time period. The switching will continue to achieve regulation.

The regulator will operate in the discontinuous conduction mode (DCM) at a light load, and the continuous conduction mode (CCM) with a heavy load. In the DCM, the current through the inductor starts at zero and ramps up to a peak during the ON-time, and then ramps back to zero before the end of the OFF-time. It remains zero and the load current is supplied entirely by the output capacitor. The next ON-time period starts when the voltage at the FB pin falls below the internal reference. The operating frequency in the DCM is lower and varies larger with the load current as compared with the CCM. Conversion efficiency is maintained because conduction loss and switching loss are reduced with the reduction in the load and the switching frequency, respectively. The operating frequency in the DCM can be calculated approximately as follows:

Equation 1. LM3102 30021321.gif

In the continuous conduction mode (CCM), the current flows through the inductor in the entire switching cycle, and never reaches zero during the OFF-time. The operating frequency remains relatively constant with load and line variations. The CCM operating frequency can be calculated approximately as follows:

Equation 2. LM3102 30021322.gif

The output voltage is set by two external resistors RFB1 and RFB2. The regulated output voltage is

Equation 3. VOUT = 0.8V x (RFB1 + RFB2)/RFB2