SLUSAU4B DECEMBER   2011  – February 2019 TPS53219A

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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 Diagram
    3. 7.3 Feature Description
      1. 7.3.1  Enable and Soft-Start
      2. 7.3.2  Adaptive ON-Time D-CAP Control and Frequency Selection
      3. 7.3.3  Small Signal Model
      4. 7.3.4  Ramp Signal
      5. 7.3.5  Adaptive Zero Crossing
      6. 7.3.6  Output Discharge Control
      7. 7.3.7  Low-Side Driver
      8. 7.3.8  High-Side Driver
      9. 7.3.9  Power Good
      10. 7.3.10 Current Sense and Overcurrent Protection
      11. 7.3.11 Overvoltage and Undervoltage Protection
      12. 7.3.12 UVLO Protection
      13. 7.3.13 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Light Load Condition in Auto-Skip Operation
      2. 7.4.2 Forced Continuous Conduction Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Typical Application With Power Block
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 External Components Selection
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Typical Application With Ceramic Output Capacitors
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 External Parts Selection With All Ceramic Output Capacitors
        3. 8.2.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.4.1 Light Load Condition in Auto-Skip Operation

While the MODE pin is pulled low through RMODE, TPS53219A automatically reduces the switching frequency at light load conditions to maintain high efficiency. Detailed operation is described as follows. 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 IO(LL) (that is, the threshold between continuous and discontinuous conduction mode) can be calculated as shown in Equation 8.

Equation 8. TPS53219A q_ioutll_lusaa8.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 IO(LL) given in Equation 8. For example, it is 60 kHz at IO(LL)/5 if the frequency setting is 300 kHz.