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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8.3.3 Ramp Signal

The TPS53318 and TPS53319 devices add a ramp signal to the 0.6-V reference in order to improve jitter performance. As described in the previous section, the feedback voltage is compared with the reference information to keep the output voltage in regulation. By adding a small ramp signal to the reference, the signal-to-noise ratio at the onset of a new switching cycle is improved. Therefore the operation becomes less jittery and more stable. The ramp signal is controlled to start with –7 mV at the beginning of an on-cycle and becomes 0 mV at the end of an off-cycle in steady state.

During skip mode operation, under discontinuous conduction mode (DCM), the switching frequency is lower than the nominal frequency and the off-time is longer than the off-time in CCM. Because of the longer off-time, the ramp signal extends after crossing 0 mV. However, it is clamped at 3 mV to minimize the DC offset.