ZHCSCA8A March   2014  – April 2019 TPS65286

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用
  3. 3 说明
    1.     Device Images
      1.      简化原理图
      2.      效率
        1.       修订历史记录
  4. 4 Pin Configuration and Functions
    1.     Pin Functions
  5. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  6. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Power Switch
        1. 6.3.1.1 Over Current Condition
        2. 6.3.1.2 Reverse Current and Voltage Protection
        3. 6.3.1.3 nFAULT1/2 Response
        4. 6.3.1.4 Under-Voltage Lockout (UVLO)
        5. 6.3.1.5 Enable and Output Discharge
        6. 6.3.1.6 Power Switch Input and Output Capacitance
        7. 6.3.1.7 Programming the Current-Limit Threshold
      2. 6.3.2 Buck DCDC Converter
        1. 6.3.2.1  Output Voltage
        2. 6.3.2.2  Clock Synchronization
        3. 6.3.2.3  Error Amplifier
        4. 6.3.2.4  Slope Compensation
        5. 6.3.2.5  Enable and Adjusting Under-Voltage Lockout
        6. 6.3.2.6  Soft-Start Time
        7. 6.3.2.7  Internal V7V Regulator
        8. 6.3.2.8  Hard Short Circuit Protection
        9. 6.3.2.9  Bootstrap Voltage (BST) and Low Dropout Operation
        10. 6.3.2.10 Thermal Performance
        11. 6.3.2.11 Loop Compensation
    4. 6.4 Device Functional Modes
      1. 6.4.1 Pulse Skipping Mode Operation
  7. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Applications
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Step by Step Design Procedure
        2. 7.2.2.2 Related Parts
        3. 7.2.2.3 Inductor Selection
        4. 7.2.2.4 Output Capacitor Selection
        5. 7.2.2.5 Input Capacitor Selection
        6. 7.2.2.6 Soft-Start Capacitor Selection
        7. 7.2.2.7 Minimum Output Voltage
        8. 7.2.2.8 Compensation Component Selection
        9. 7.2.2.9 Auto-Retry Functionality of USB Switches
      3. 7.2.3 Application Performance Plots
  8. 8 Power Supply Recommendations
  9. 9 Layout
    1. 9.1 Layout Guidelines
    2. 9.2 Layout Example
  10. 10器件和文档支持
    1. 10.1 器件支持
      1. 10.1.1 第三方产品免责声明
    2. 10.2 接收文档更新通知
    3. 10.3 社区资源
    4. 10.4 商标
    5. 10.5 静电放电警告
    6. 10.6 术语表
  11. 11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

7.2.2.4 Output Capacitor Selection

There are two primary considerations for selecting the value of the output capacitor. The output capacitors are selected to meet load transient and output ripple’s requirements. Equation 15 gives the minimum output capacitance to meet the transient specification. For this example, Lo = 4.7 µH, ΔIOUT = 3 A – 0 A = 3 A and ΔVOUT = 250 mV (5% of regulated 5 V). Using these numbers gives a minimum capacitance of 34 µF. A standard 4 x 22 µF ceramic is chose in the design.

Equation 15. TPS65286 eq15_Co_slvsca4.gif

The selection of COUT is driven by the effective series resistance (ESR). Equation 16 calculates the minimum output capacitance needed to meet the output voltage ripple specification. Where fSW is the switching frequency, ΔVOUT is the maximum allowable output voltage ripple, and ΔiL is the inductor ripple current. In this case, the maximum output voltage ripple is 40 mV (1% of regulated 5 V). From Equation 16, the output current ripple is
1.7 A and the minimum output capacitance meeting the output voltage ripple requirement is 12.2 µF with 3-mΩ ESR resistance.

Equation 16. TPS65286 eq16_Co_slvsca4.gif

After considering both requirements, for this example, four 22-µF 6.3-V X7R ceramic capacitors with 3-mΩ of ESR will be used. Equation 17 calculates the maximum ESR an output capacitor can have to meet the output voltage ripple specification. Equation 17 indicates the ESR should be less than 23.5 mΩ. In this case, the ceramic capacitors’ ESR is much smaller than 23.5 mΩ.

Equation 17. TPS65286 eq17_Resr_slvsca4.gif

Additional capacitance de-ratings for aging, temperature and DC bias should be factored in which increases this minimum value. For this example, a 47-µF 6.3-V X5R ceramic capacitor with 3-mΩ of ESR is be used. Capacitors generally have limits to the amount of ripple current they can handle without failing or producing excess heat. An output capacitor that can support the inductor ripple current must be specified. Some capacitor data sheets specify the root mean square (RMS) value of the maximum ripple current. Equation 18 can be used to calculate the RMS ripple current the output capacitor needs to support. For this application, Equation 18 yields 486 mA.

Equation 18. TPS65286 eq18_Icorms_slvsca4.gif