ZHCSI85A May   2018  – July 2019 LM26420-Q1

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      LM26420 双路降压直流/直流转换器
      2.      LM26420 效率（高达 93%）
  4. 4 修订历史记录
  5. 5 Pin Configuration and Functions
    1.     Pin Functions: 16-Pin WQFN
    2.     Pin Functions 20-Pin HTSSOP
  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 Per Buck
    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 Soft Start
      2. 7.3.2 Power Good
      3. 7.3.3 Precision Enable
    4. 7.4 Device Functional Modes
      1. 7.4.1 Output Overvoltage Protection
      2. 7.4.2 Undervoltage Lockout
      3. 7.4.3 Current Limit
      4. 7.4.4 Thermal Shutdown
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Programming Output Voltage
      2. 8.1.2 VINC Filtering Components
      3. 8.1.3 Using Precision Enable and Power Good
      4. 8.1.4 Overcurrent Protection
    2. 8.2 Typical Applications
      1. 8.2.1 2.2-MHz, 0.8-V Typical High-Efficiency Application Circuit
        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 Inductor Selection
          3. 8.2.1.2.3 Input Capacitor Selection
          4. 8.2.1.2.4 Output Capacitor
          5. 8.2.1.2.5 Calculating Efficiency and Junction Temperature
        3. 8.2.1.3 Application Curves
      2. 8.2.2 2.2-MHz, 1.8-V Typical High-Efficiency Application Circuit
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
      3. 8.2.3 LM26420-Q12.2-MHz, 2.5-V Typical High-Efficiency Application Circuit
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
        3. 8.2.3.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Considerations
      1. 10.3.1 Method 1: Silicon Junction Temperature Determination
      2. 10.3.2 Thermal Shutdown Temperature Determination
  11. 11器件和文档支持
    1. 11.1 器件支持
      1. 11.1.1 第三方米6体育平台手机版_好二三四免责声明
      2. 11.1.2 使用 WEBENCH® 工具创建定制设计
    2. 11.2 文档支持
      1. 11.2.1 相关文档
    3. 11.3 接收文档更新通知
    4. 11.4 社区资源
    5. 11.5 商标
    6. 11.6 静电放电警告
    7. 11.7 Glossary
  12. 12机械、封装和可订购信息

7.3.1 Soft Start

This function forces VOUT to increase at a controlled rate during start-up in a controlled fashion, which helps reduce inrush current and eliminate overshoot on VOUT. During soft start, reference voltage of the error amplifier ramps from 0 V to its nominal value of 0.8 V in approximately 600 µs. If the converter is turned on into a pre-biased load, then the feedback begins ramping from the prebias voltage but at the same rate as if it had started from 0 V. The two outputs start up ratiometrically if enabled at the same time, see Figure 27 below.

LM26420-Q1 LM26420_Soft_Start.gif
Figure 27. LM26420 Soft-Start
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