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

7.2.2.3 Inductor Selection

The higher operating frequency allows the use of smaller inductor and capacitor values. A higher frequency generally results in lower efficiency because of MOSFET gate charge losses. In addition to this basic trade-off, the effect of inductor value on ripple current and low current operation must also be considered. The ripple current depends on the inductor value. The inductor ripple current iL decreases with higher inductance or higher frequency and increases with higher input voltage VIN. Accepting larger values of iL allows the use of low inductances, but results in higher output voltage ripple and greater core losses.

To calculate the value of the output inductor, use Equation 11. LIR is a coefficient that represents inductor peak-to-peak ripple to DC load current. LIR is suggested to choose to 0.1 ~ 0.3 for most applications.

Actual core loss of inductor is independent of core size for a fixed inductor value, but it is very dependent on inductance value selected. As inductance increases, core losses go down. Unfortunately, increased inductance requires more turns of wire and therefore copper losses will increase. Ferrite designs have very low core loss and are preferred for high switching frequencies, so design goals can concentrate on copper loss and preventing saturation. Ferrite core material saturates hard, which means that inductance collapses abruptly when the peak design current is exceeded. It results in an abrupt increase in inductor ripple current and consequent output voltage ripple. Do not allow the core to saturate. It is important that the RMS current and saturation current ratings are not exceeding the inductor specification. The RMS and peak inductor current can be calculated from Equation 13 and Equation 14.

Equation 11. TPS65286 eq11_L_slvsca4.gif
Equation 12. TPS65286 eq12_iL_slvsca4.gif
Equation 13. TPS65286 eq13_iLrms_slvsca4.gif
Equation 14. TPS65286 eq14_iLpeak_slvsca4.gif

For this design example, use LIR = 0.3 and the inductor is calculated to be 4.40 µH with VIN = 24 V. Choose 4.7 µH value of the standard inductor, the peak to peak inductor ripple is about 28.1% of 6-A DC load current.