JAJSNB5B July   2023  – June 2024 TPSM828301 , TPSM828302 , TPSM828303

PRODMIX  

  1.   1
  2. 1 特長
  3. 2 アプリケーション
  4. 3 概要
  5. 4 Device Options
  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 RDS Package
    5. 6.5 Thermal Information VCB Package
    6. 6.6 Electrical Characteristics
    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 Pulse Width Modulation (PWM) Operation
      2. 7.3.2 Power Save Mode (PSM) Operation
      3. 7.3.3 Start-Up and Soft Start
      4. 7.3.4 Switch Cycle-by-Cycle Current Limit
      5. 7.3.5 Undervoltage Lockout
      6. 7.3.6 Thermal Shutdown
      7. 7.3.7 Optimized EMI Performance
    4. 7.4 Device Functional Modes
      1. 7.4.1 Enable, Disable, and Output Discharge
      2. 7.4.2 Minimum Duty Cycle and 100% Mode Operation
      3. 7.4.3 Power Good
  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 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 Setting The Output Voltage
        3. 8.2.2.3 Input Capacitor Selection
        4. 8.2.2.4 Output Capacitor Selection
      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
        1. 8.4.2.1 Thermal Considerations
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
      1. 9.1.1 サード・パーティ製品に関する免責事項
      2. 9.1.2 Development Support
        1. 9.1.2.1 Custom Design With WEBENCH® Tools
    2. 9.2 Documentation Support
      1. 9.2.1 Related Documentation
    3. 9.3 サポート・リソース
    4. 9.4 Trademarks
    5. 9.5 静電気放電に関する注意事項
    6. 9.6 用語集
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

7.3.2 Power Save Mode (PSM) Operation

To maintain high efficiency at light loads, the device enters power save mode (PSM) at the boundary to discontinuous conduction mode (DCM). This event happens when the output current becomes smaller than half of the ripple current of the inductor. The device operates with a fixed on-time, and the switching frequency decreases proportional to the load current as shown in Figure 7-2. Calculate as:

Equation 2. fPSM=2×IOUTTON2×VINVOUTVIN-VOUTL

Use L=470nH for the RDS package and L=340nH for the VCB package.

TPSM828301 TPSM828302 TPSM828303 Discontinuous Conduction Mode (PSM-DCM) Current WaveformFigure 7-2 Discontinuous Conduction Mode (PSM-DCM) Current Waveform

In PSM, the output voltage rises slightly above the nominal target, which can be minimized using larger output capacitance. At duty cycles larger than 90%, the device does not enter PSM and maintains output regulation in PWM mode.