ZHCS979F June   2012  – October 2020 TPS53318 , TPS53319

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
    7. 7.7 TPS53319 Typical Characteristics
    8. 7.8 TPS53318 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1  5-V LDO and VREG Start-Up
      2. 8.3.2  Adaptive On-Time D-CAP Control and Frequency Selection
      3. 8.3.3  Ramp Signal
      4. 8.3.4  Adaptive Zero Crossing
      5. 8.3.5  Output Discharge Control
      6. 8.3.6  Power-Good
      7. 8.3.7  Current Sense, Overcurrent, and Short Circuit Protection
      8. 8.3.8  Overvoltage and Undervoltage Protection
      9. 8.3.9  Redundant Overvoltage Protection (OVP)
      10. 8.3.10 UVLO Protection
      11. 8.3.11 Thermal Shutdown
      12. 8.3.12 Small Signal Model
      13. 8.3.13 External Component Selection Using All Ceramic Output Capacitors
    4. 8.4 Device Functional Modes
      1. 8.4.1 Enable, Soft Start, and Mode Selection
      2. 8.4.2 Auto-Skip Eco-mode Light Load Operation
      3. 8.4.3 Forced Continuous Conduction Mode
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Application Using Bulk Output Capacitors, Redundant Overvoltage Protection Function (OVP) Disabled
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Step One: Select Operation Mode and Soft-Start Time
          2. 9.2.1.2.2 Step Two: Select Switching Frequency
          3. 9.2.1.2.3 Step Three: Choose the Inductor
          4. 9.2.1.2.4 Step Four: Choose the Output Capacitor or Capacitors
          5. 9.2.1.2.5 Step Five: Determine the Value of R1 and R2
          6. 9.2.1.2.6 Step Six: Choose the Overcurrent Setting Resistor
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Application Using Ceramic Output Capacitors, Redundant Overvoltage Protection Function (OVP) Enabled
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
          1. 9.2.2.2.1 External Component Selection Using All Ceramic Output Capacitors
          2. 9.2.2.2.2 Redundant Overvoltage Protection
        3. 9.2.2.3 Application Curves
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Development Support
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

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8.4.2 Auto-Skip Eco-mode Light Load Operation

While RMODE pulls the MODE pin low, the controller automatically reduces the switching frequency at light-load conditions to maintain high efficiency. More specifically, as the output current decreases from heavy load condition, the inductor current is also reduced and eventually comes to the point that its rippled valley touches zero level, which is the boundary between continuous conduction and discontinuous conduction modes. The synchronous MOSFET is turned off when this zero inductor current is detected. As the load current further decreases, the converter runs into discontinuous conduction mode (DCM). The on-time is kept almost the same as it was in the continuous conduction mode so that it takes longer time to discharge the output capacitor with smaller load current to the level of the reference voltage. The transition point to the light-load operation IOUT(LL) (that is, the threshold between continuous and discontinuous conduction mode) can be calculated as shown in Equation 13.

Equation 13. GUID-DB1A3734-74E7-4D2A-A698-A6659A0FC715-low.gif

where

  • ƒSW is the PWM switching frequency

Switching frequency versus output current in the light-load condition is a function of L, VIN and VOUT, but it decreases almost proportionally to the output current from the IOUT(LL) given in Equation 13. For example, it is 60 kHz at IOUT(LL)/5 if the frequency setting is 300 kHz.