ZHCSHM2D June   2018  – April 2025 TPS746-Q1

PRODUCTION DATA  

  1.   1
  2. 1 特性
  3. 2 应用
  4. 3 说明
  5. 4 Pin Configuration and Functions
  6. 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 Timing Requirements
    7. 5.7 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagrams
    3. 6.3 Feature Description
      1. 6.3.1 Undervoltage Lockout (UVLO)
      2. 6.3.2 Shutdown
      3. 6.3.3 Foldback Current Limit
      4. 6.3.4 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Normal Operation
      2. 6.4.2 Dropout Operation
      3. 6.4.3 Disabled
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Adjustable Device Feedback Resistors
      2. 7.1.2 Input and Output Capacitor Selection
      3. 7.1.3 Dropout Voltage
      4. 7.1.4 Exiting Dropout
      5. 7.1.5 Reverse Current
      6. 7.1.6 Power Dissipation (PD)
      7. 7.1.7 Power-Good Function
      8. 7.1.8 Feed-Forward Capacitor (CFF)
      9. 7.1.9 Start-Up Sequencing
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Input Current
        2. 7.2.2.2 Thermal Dissipation
      3. 7.2.3 Application Curve
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Examples
  9. 8 Device and Documentation Support
    1. 8.1 Device Support
      1. 8.1.1 Device Nomenclature
    2. 8.2 Documentation Support
      1. 8.2.1 Related Documentation
    3. 8.3 接收文档更新通知
    4. 8.4 支持资源
    5. 8.5 Trademarks
    6. 8.6 静电放电警告
    7. 8.7 术语表
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

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7.1.4 Exiting Dropout

Some applications have transients that place the LDO into dropout, such as slower ramps on VIN during start-up. As with other LDOs, the output may overshoot on recovery from these conditions. A ramping input supply causes an LDO to overshoot on start-up, as shown in Figure 7-2, when the slew rate and voltage levels are in the correct range. Use an enable signal to avoid this condition.

TPS746-Q1 Start-Up Into Dropout Figure 7-2 Start-Up Into Dropout

Line transients out of dropout can also cause overshoot on the output of the regulator. These overshoots are caused by the error amplifier having to drive the gate capacitance of the pass element and bring the gate back to the correct voltage for proper regulation. Figure 7-3 illustrates what is happening internally with the gate voltage and how overshoot can be caused during operation. When the LDO is placed in dropout, the gate voltage (VGS) is pulled all the way down to ground to give the pass device the lowest on-resistance as possible. However, if a line transient occurs when the device is in dropout, the loop is not in regulation and can cause the output to overshoot until the loop responds and the output current pulls the output voltage back down into regulation. If these transients are not acceptable, then continue to add input capacitance in the system until the transient is slow enough to reduce the overshoot.

TPS746-Q1 Line Transients From Dropout Figure 7-3 Line Transients From Dropout