ZHCSHF3C january   2018  – may 2023 TPS65268-Q1

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 描述
  5. 4 Revision History
  6. 5 Pin Configuration and Functions
  7. 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 Timing Requirements
    7. 6.7 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Adjusting the Output Voltage
      2. 7.3.2  Enable and Adjusting UVLO
      3. 7.3.3  Soft-Start Time
      4. 7.3.4  Power-Up Sequencing
      5. 7.3.5  V7V Low-Dropout Regulator and Bootstrap
      6. 7.3.6  Out-of-Phase Operation
      7. 7.3.7  Output Overvoltage Protection (OVP)
      8. 7.3.8  Slope Compensation
      9. 7.3.9  Overcurrent Protection
        1. 7.3.9.1 High-Side MOSFET Overcurrent Protection
        2. 7.3.9.2 Low-Side MOSFET Overcurrent Protection
      10. 7.3.10 Power Good
        1. 7.3.10.1 Adjustable Switching Frequency
      11. 7.3.11 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Normal Operation
      2. 7.4.2 Standby Operation
  9. 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 Output Inductor Selection
        2. 8.2.2.2 Output Capacitor Selection
        3. 8.2.2.3 Input Capacitor Selection
        4. 8.2.2.4 Loop Compensation
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 接收文档更新通知
    2. 9.2 支持资源
    3. 9.3 Trademarks
    4. 9.4 静电放电警告
    5. 9.5 术语表
  11. 10Mechanical, Packaging, and Orderable Information

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7.3.5 V7V Low-Dropout Regulator and Bootstrap

Power for the high-side and low-side MOSFET drivers and most other internal circuitry is derived from the V7V pin. The internal built-in low-dropout (LDO) linear regulator supplies 4.96 V (typical) from 5 V VIN to the V7V voltage. The user must connect a 10-µF ceramic capacitor from the V7V pin to power ground.

If the input voltage decreases to the UVLO threshold voltage, the UVLO comparator detects the V7V pin voltage and forces the converter off.

Each high-side MOSFET driver is biased from the floating bootstrap capacitor, CB, shown in Figure 7-8, which is normally recharged during each cycle through an internal low-side MOSFET or the body diode of a low-side MOSFET when the high-side MOSFET turns off. The boot capacitor is charged when the BST pin voltage is less than the input voltage and the BST-LX voltage is below regulation. TI recommends using a 47-nF ceramic capacitor. TI recommends using a ceramic capacitor with an X7R or X5R grade dielectric with a voltage rating of 10 V or higher because of the stable characteristics over temperature and voltage. Each low-side MOSFET driver is powered from the V7V pin directly.

To improve dropout, the device is designed to operate at 100% duty cycle as long as the BST to LXx pin voltage is greater than the BST-LX UVLO threshold, which is typically 2.1 V. When the voltage between the BST and LXx pins drops below the BST-LX UVLO threshold, the high-side MOSFET is turned off and the low-side MOSFET is turned on allowing the boot capacitor to be recharged.

GUID-20230502-SS0I-XLMB-BMM6-RFVLQ8HMCK1P-low.svg Figure 7-8 V7V Linear Dropout Regulator and Bootstrap Voltage Diagram