SLVSEW4 April   2019 TPS650002-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Typical Application 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 Switching Characteristics
    7. 6.7 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 Step-Down Converter
      2. 7.3.2 Soft Start
      3. 7.3.3 Linear Regulators
      4. 7.3.4 Power Good
    4. 7.4 Device Functional Modes
  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 Output Filter Design (Inductor and Output Capacitor)
          1. 8.2.2.1.1 Inductor Selection
          2. 8.2.2.1.2 Output Capacitor Selection
        2. 8.2.2.2 Input Capacitor Selection
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Third-Party Products Disclaimer
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 Community Resources
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.2.2.1.1 Inductor Selection

The typical value for the converter inductor is 2.2-μH output inductor. Larger or smaller inductor values in the range of 1.5 μH to 3.3 μH can optimize the performance of the device for specific operation conditions. The selected inductor must be rated for its DC resistance and saturation current. The DC resistance of the inductance influences the efficiency of the converter directly. An inductor with lowest DC resistance must be selected for highest efficiency. For more information on inductor selection, refer to the Choosing Inductors and Capacitors for DC/DC Converters application report.

Equation 1 calculates the maximum inductor current under static load conditions. The saturation current of the inductor should be rated higher than the maximum inductor current as calculated with Equation 2. TI recommends this because during heavy load transient, the inductor current rises above the calculated value.

Equation 1. TPS650002-Q1 eq_il_lvs810.gif

where

  • f = Switching Frequency (2.25-MHz typical)
  • L = Inductor Value
  • ΔIL = Peak-to-peak Inductor Ripple Current
Equation 2. TPS650002-Q1 eq_ilmax_lvs810.gif

where

  • ILmax = Maximum Inductor Current

The highest inductor current occurs at maximum VIN.

Open-core inductors have a soft saturation characteristic and can usually handle higher inductor currents versus a comparable shielded inductor.

A more conservative approach is to select the inductor current rating just for the maximum switch current of the corresponding converter. Consider that the core material from inductor to inductor differs and impacts the efficiency especially at high-switching frequencies.

The step down converter has internal loop compensation. TI designed the internal loop compensation to work with a certain output filter corner frequency calculated as in Equation 3:

Equation 3. TPS650002-Q1 eq_fc_lvs810.gif

The selection of external L-C filter must be consistent with Equation 3. The product of L × COUT must be constant while selecting smaller inductor or increasing output capacitor value.