SLVSDT1C July   2017  – June 2020 TPSM82480

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application space
      2.      Efficiency vs Output Current space space
  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 Shutdown (EN)
      2. 7.3.2  Soft-Start (SS), Pre-biased Output
      3. 7.3.3  Tracking (TR)
      4. 7.3.4  Output Voltage Select (VSEL)
      5. 7.3.5  Forced PWM (MODE)
      6. 7.3.6  Power Good (PG)
      7. 7.3.7  Thermal Good (TG)
      8. 7.3.8  Active Output Discharge
      9. 7.3.9  Undervoltage Lockout (UVLO)
      10. 7.3.10 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Pulse Width Modulation (PWM) Operation
      2. 7.4.2 Power Save Mode (PSM) Operation
      3. 7.4.3 Minimum Duty Cycle and 100% Mode Operation
      4. 7.4.4 Phase Shifted Operation
      5. 7.4.5 Phase Add/Shed and Current Balancing
      6. 7.4.6 Current Limit and Short Circuit Protection
  8. 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 Setting the Output Voltage
        2. 8.2.2.2 Setting VOUT2 Using the VSEL Feature
        3. 8.2.2.3 Feedforward Capacitance
        4. 8.2.2.4 Output Capacitor Selection
        5. 8.2.2.5 Input Capacitor Selection
        6. 8.2.2.6 Soft-Start Capacitor Selection
        7. 8.2.2.7 Tracking
        8. 8.2.2.8 Thermal Good
      3. 8.2.3 Application Curves
    3. 8.3 System Examples
  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 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
    1. 12.1 Tape and Reel Information

Package Options

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

7.4.3 Minimum Duty Cycle and 100% Mode Operation

The minimum on-time, which is typically 70ns, normally determines a limit on the minimum operating duty cycle. The calculation is:

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Equation 2. TPSM82480 SLVSCL9_eqdcmin.gif

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However, a frequency foldback lowers the switching frequency depending on the duty cycle and ensures proper regulation for every duty cycle.

There is no limit towards maximum duty cycle. When the input voltage becomes close to the output voltage, the device enters automatically 100% duty cycle mode and both high-side FETs switch on as long as VOUT remains lower than the regulation setpoint. In this case, the voltage drop across the high-side FETs and the inductors determines the output voltage level. An estimate for the minimum input voltage to maintain output voltage regulation is:

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Equation 3. TPSM82480 SLVSDT1_eqvinmin.gif

where

  • typical DCR of each inductor is 20 mΩ
  • the maximum DCR of each inductor is 27 mΩ

In 100% duty cycle mode, the low-side FETs are switched off. The typical quiescent current in 100% mode is
3.5 mA.