SLUSBN5C August   2013  – February 2026 TPS53515

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  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 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1  5V LDO and VREG Start-Up
      2. 6.3.2  Enable, Soft Start, and Mode Selection
      3. 6.3.3  Frequency Selection
      4. 6.3.4  D-CAP3 Control and Mode Selection
        1. 6.3.4.1 D-CAP3™ Control Mode
        2. 6.3.4.2 Sample and Hold Circuitry
        3. 6.3.4.3 Adaptive Zero-Crossing
      5. 6.3.5  Power-Good
      6. 6.3.6  Current Sense and Overcurrent Protection
      7. 6.3.7  Overvoltage and Undervoltage Protection
      8. 6.3.8  Out-of-Bounds Operation
      9. 6.3.9  UVLO Protection
      10. 6.3.10 Thermal Shutdown
    4. 6.4 Device Functional Modes
      1. 6.4.1 Auto-Skip Eco-mode Light Load Operation
      2. 6.4.2 Forced Continuous-Conduction Mode
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Choose the Switching Frequency
        2. 7.2.2.2 Choose the Operation Mode
        3. 7.2.2.3 Choose the Inductor
        4. 7.2.2.4 Choose the Output Capacitor
        5. 7.2.2.5 Determine the Value of R1 and R2
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
      3. 7.4.3 Thermal Performance
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

6.4.1 Auto-Skip Eco-mode Light Load Operation

While the MODE pin is pulled to GND directly or through 150kΩ resistor, the TPS53515 device automatically reduces the switching frequency at light-load conditions to maintain high efficiency. This section describes the operation in detail.

As the output current decreases from heavy load condition, the inductor current also decreases until the rippled valley of the inductor current touches zero level. Zero level is the boundary between the continuous-conduction and discontinuous-conduction modes. The synchronous MOSFET turns off when this zero inductor current is detected. As the load current decreases further, the converter runs into discontinuous-conduction mode (DCM). The on-time is maintained to a level approximately the same as during continuous-conduction mode operation so that discharging the output capacitor with a smaller load current to the level of the reference voltage requires more time. The transition point to the light-load operation IO(LL) (for example: the threshold between continuous- and discontinuous-conduction mode) is calculated as shown in Equation 6.

Equation 6. TPS53515

where

  • fSW is the PWM switching frequency

Using only ceramic capacitors is recommended for Auto-skip mode.