JAJSL23B January   2021  – January 2022 TPS785-Q1

PRODUCTION DATA  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
  4. 4 Revision History
  5. 5 Pin Configuration and 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 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1 Foldback Current Limit
      2. 7.3.2 Output Enable
      3. 7.3.3 Active Discharge
      4. 7.3.4 Undervoltage Lockout (UVLO) Operation
      5. 7.3.5 Dropout Voltage
      6. 7.3.6 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Device Functional Mode Comparison
      2. 7.4.2 Normal Operation
      3. 7.4.3 Dropout Operation
      4. 7.4.4 Disabled
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Recommended Capacitor Types
      2. 8.1.2 Input and Output Capacitor Requirements
      3. 8.1.3 Adjustable Device Feedback Resistors
      4. 8.1.4 Load Transient Response
      5. 8.1.5 Exiting Dropout
      6. 8.1.6 Dropout Voltage
      7. 8.1.7 Reverse Current
      8. 8.1.8 Feed-Forward Capacitor (CFF)
      9. 8.1.9 Power Dissipation (PD)
        1. 8.1.9.1 Estimating Junction Temperature
        2. 8.1.9.2 Recommended Area for Continuous Operation
        3. 8.1.9.3 Power Dissipation versus Ambient Temperature
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
      3. 8.2.3 Application Curve
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Additional Layout Considerations
    2. 10.2 Layout Examples
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Device Nomenclature
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 サポート・リソース
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

8.1.4 Load Transient Response

The load-step transient response is the output voltage response by the LDO to a step in load current, whereby output voltage regulation is maintained. There are two key transitions during a load transient response: the transition from a light to a heavy load and the transition from a heavy to a light load. The regions shown in Figure 8-2 are broken down as follows. Regions A, E, and H are where the output voltage is in steady-state.

GUID-25712BD2-0569-468F-A4C1-1B6187DCFD8D-low.gifFigure 8-2 Load Transient Waveform

During transitions from a light load to a heavy load, the:

  • Initial voltage dip is a result of the depletion of the output capacitor charge and parasitic impedance to the output capacitor (region B)
  • Recovery from the dip results from the LDO increasing its sourcing current, and leads to output voltage regulation (region C)

  • Initial voltage rise results from the LDO sourcing a large current, and leads to the output capacitor charge to increase (region F)
  • Recovery from the rise results from the LDO decreasing its sourcing current in combination with the load discharging the output capacitor (region G)

A larger output capacitance reduces the peaks during a load transient but slows down the response time of the device. A larger DC load also reduces the peaks because the amplitude of the transition is lowered and a higher current discharge path is provided for the output capacitor.