ZHCSIJ1E June   1999  – July 2018 LM2574 , LM2574HV

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      典型应用（固定输出电压版本）
  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 for All Output Voltage Versions
    6. 6.6  Electrical Characteristics – 3.3-V Version
    7. 6.7  Electrical Characteristics – 5-V Version
    8. 6.8  Electrical Characteristics – 12-V Version
    9. 6.9  Electrical Characteristics – 15-V Version
    10. 6.10 Electrical Characteristics – Adjustable Version
    11. 6.11 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 Current Limit
      2. 7.3.2 Undervoltage Lockout
      3. 7.3.3 Delayed Start-Up
      4. 7.3.4 Adjustable Output, Low-Ripple Power Supply
    4. 7.4 Device Functional Modes
      1. 7.4.1 Shutdown Mode
      2. 7.4.2 Active Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Input Capacitor (CIN)
      2. 8.1.2 Inductor Selection
      3. 8.1.3 Inductor Ripple Current
      4. 8.1.4 Output Capacitor
      5. 8.1.5 Catch Diode
      6. 8.1.6 Output Voltage Ripple and Transients
      7. 8.1.7 Feedback Connection
      8. 8.1.8 ON/OFF Input
      9. 8.1.9 Additional Applications
        1. 8.1.9.1 Inverting Regulator
        2. 8.1.9.2 Negative Boost Regulator
    2. 8.2 Typical Applications
      1. 8.2.1 Fixed Output Voltage Applications
        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 (L1)
          3. 8.2.1.2.3 Output Capacitor Selection (COUT)
          4. 8.2.1.2.4 Catch Diode Selection (D1)
          5. 8.2.1.2.5 Input Capacitor (CIN)
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Adjustable Output Voltage Applications
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Programming Output Voltage
          2. 8.2.2.2.2 Inductor Selection (L1)
          3. 8.2.2.2.3 Output Capacitor Selection (COUT)
          4. 8.2.2.2.4 Catch Diode Selection (D1)
          5. 8.2.2.2.5 Input Capacitor (CIN)
        3. 8.2.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Grounding
    4. 10.4 Thermal Considerations
  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
      3. 11.1.3 器件命名规则
        1. 11.1.3.1  降压稳压器
        2. 11.1.3.2  降压/升压稳压器
        3. 11.1.3.3  占空比 (D)
        4. 11.1.3.4  环流二极管或导流二极管
        5. 11.1.3.5  电容器等效串联电阻 (ESR)
        6. 11.1.3.6  等效串联电感 (ESL)
        7. 11.1.3.7  输出纹波电压
        8. 11.1.3.8  电容器纹波电流
        9. 11.1.3.9  待机静态电流 (ISTBY)
        10. 11.1.3.10 电感器纹波电流 (ΔiIND)
        11. 11.1.3.11 连续与非连续模式运行
        12. 11.1.3.12 电感器饱和
        13. 11.1.3.13 运算伏特微秒常数 (E × Top)
    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 术语表
  12. 12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

8.2.2.2.1 Programming Output Voltage

Selecting R1 and R2, as shown in Figure 27.

Use Equation 7 to select the appropriate resistor values.

Equation 7. LM2574 LM2574HV eq_vout_snvs104.gif

where

  • VREF = 1.23 V

R1 can be between 1k and 5k as in Equation 8. For best temperature coefficient and stability with time, use 1% metal film resistors.

Equation 8. LM2574 LM2574HV eq_r2_snvs104.gif

For this example, use Equation 9 and Equation 10.

Equation 9. LM2574 LM2574HV eq_vout_123_snvs104.gif

where

  • R1 = 1k
Equation 10. LM2574 LM2574HV eq_r2_realvalues_snvs104.gif

R2 = 1k (19.51−1) = 18.51k, closest 1% value is 18.7k
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