ZHCS573I August   2010  – April 2018 LM25119

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      典型应用电路
  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 Switching Characteristics
    7. 6.7 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  High Voltage Start-Up Regulator
      2. 7.3.2  UVLO
      3. 7.3.3  Enable 2
      4. 7.3.4  Oscillator and Sync Capability
      5. 7.3.5  Error Amplifiers and PWM Comparators
      6. 7.3.6  Ramp Generator
      7. 7.3.7  Current Limit
      8. 7.3.8  Hiccup Mode Current Limiting
      9. 7.3.9  Soft Start
      10. 7.3.10 HO and LO Output Drivers
      11. 7.3.11 Maximum Duty Cycle
      12. 7.3.12 Thermal Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Diode Emulation
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Miscellaneous Functions
      2. 8.1.2 Interleaved Two-Phase Operation
      3. 8.1.3 Interleaved 4-Phase Operation
    2. 8.2 Typical Applications
      1. 8.2.1 Dual-output Design Example
        1. 8.2.1.1 Design Requirements
          1. 8.2.1.1.1 External Components
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1  Timing Resistor
          2. 8.2.1.2.2  Output Inductor
          3. 8.2.1.2.3  Current Sense Resistor
          4. 8.2.1.2.4  Ramp Resistor and Ramp Capacitor
          5. 8.2.1.2.5  Output Capacitors
          6. 8.2.1.2.6  Input Capacitors
          7. 8.2.1.2.7  VCC Capacitor
          8. 8.2.1.2.8  Bootstrap Capacitor
          9. 8.2.1.2.9  Soft Start Capacitor
          10. 8.2.1.2.10 Restart Capacitor
          11. 8.2.1.2.11 Output Voltage Divider
          12. 8.2.1.2.12 UVLO Divider
          13. 8.2.1.2.13 MOSFET Selection
          14. 8.2.1.2.14 MOSFET Snubber
          15. 8.2.1.2.15 Error Amplifier Compensation
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Two-Phase Design Example
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
        3. 8.2.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Switching Jitter Root Causes and Solutions
    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 Glossary
  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

8.2.1.2.5 Output Capacitors

The output capacitors smooth the inductor ripple current and provide a source of charge during transient loading conditions. For this design example, a 680-µF electrolytic capacitor with 10-mΩ ESR was selected as the main output capacitor. The fundamental component of the output ripple voltage is approximated with Equation 21 and the example (Equation 22 and Equation 23).

Equation 21. LM25119 30126242.gif
Equation 22. LM25119 30126243.gif
Equation 23. LM25119 30126241.gif

Two 22-µF low ERS or ESL ceramic capacitors are placed in parallel with the 680-µF electrolytic capacitor, to further reduce the output voltage ripple and spikes.

Table 1. Performance Variation by K Factor

K < 1 1 <— K —> 3 K > 3
Cross talk Sub-harmonic oscillation may occur Higher Lower Introduces additional pole near cross-over frequency
Peak inductor current with short output condition Lower Higher
Inductor size Smaller Larger
Power dissipation of Rs Higher Lower
Efficiency Lower Higher