ZHCSBB1D July   2013  – March 2018 UCC28740

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      简化应用示意图
      2.      典型伏安图
  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 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 Detailed Pin Description
      2. 7.3.2 Valley-Switching and Valley-Skipping
      3. 7.3.3 Startup Operation
      4. 7.3.4 Fault Protection
    4. 7.4 Device Functional Modes
      1. 7.4.1 Secondary-Side Optically Coupled Constant-Voltage (CV) Regulation
      2. 7.4.2 Primary-Side Constant-Current (CC) Regulation
  8. 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 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Standby Power Estimate and No-Load Switching Frequency
        3. 8.2.2.3 Input Bulk Capacitance and Minimum Bulk Voltage
        4. 8.2.2.4 Transformer Turns-Ratio, Inductance, Primary Peak Current
        5. 8.2.2.5 Transformer Parameter Verification
        6. 8.2.2.6 VS Resistor Divider, Line Compensation
        7. 8.2.2.7 Output Capacitance
        8. 8.2.2.8 VDD Capacitance, CVDD
        9. 8.2.2.9 Feedback Network Biasing
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 VDD Pin
      2. 10.1.2 VS Pin
      3. 10.1.3 FB Pin
      4. 10.1.4 GND Pin
      5. 10.1.5 CS Pin
      6. 10.1.6 DRV Pin
      7. 10.1.7 HV Pin
    2. 10.2 Layout Example
  11. 11器件和文档支持
    1. 11.1 器件支持
      1. 11.1.1 开发支持
        1. 11.1.1.1 使用 WEBENCH® 工具定制设计方案
      2. 11.1.2 器件命名规则
        1. 11.1.2.1  电容术语（以法拉为单位）
        2. 11.1.2.2  占空比术语
        3. 11.1.2.3  频率术语（以赫兹为单位）
        4. 11.1.2.4  电流术语（以安培为单位）
        5. 11.1.2.5  电流和电压调节术语
        6. 11.1.2.6  变压器术语
        7. 11.1.2.7  功率术语（以瓦特为单位）
        8. 11.1.2.8  电阻术语（以 Ω 为单位）
        9. 11.1.2.9  时序术语（以秒为单位）
        10. 11.1.2.10 电压术语（以伏特为单位）
        11. 11.1.2.11 交流电压术语（以 VRMS 为单位）
        12. 11.1.2.12 效率术语
    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

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

8.2.2.7 Output Capacitance

The output capacitance value is often determined by the transient-response requirement from the no-load condition. For example, in typical low-power USB-charger applications, there is a requirement to maintain a minimum transient VO of 4.1 V with a load-step ITRAN from 0 mA to 500 mA. Yet new higher-performance applications require smaller transient voltage droop VOΔ with ITRAN of much greater amplitude (such as from no-load to full-load), which drives the need for high-speed opto-coupled voltage feedback.

Equation 26. UCC28740 q_Cout_lusbf3.gif

where

  • tRESP is the time delay from the moment ITRAN is applied to the moment when IFB falls below 1 µA

Additional considerations for the selection of appropriate output capacitors include ripple-current, ESR, and ESL ratings necessary to meet reliability and ripple-voltage requirements. Detailed design criteria for these considerations are beyond the scope of this datasheet.