SLUSFG7 April   2025 TPS62A02-Q1 , TPS62A02A-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Device Comparison Table
  6. 5 Pin Configuration and Functions
  7. 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
  8. 7 Typical Characteristics
  9. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Power Save Mode
      2. 8.3.2 100% Duty Cycle Low Dropout Operation
      3. 8.3.3 Soft Start
      4. 8.3.4 Switch Current Limit and Short-Circuit Protection (HICCUP)
      5. 8.3.5 Undervoltage Lockout
      6. 8.3.6 Thermal Shutdown
    4. 8.4 Device Functional Modes
      1. 8.4.1 Enable and Disable
      2. 8.4.2 Power Good
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Setting the Output Voltage
        2. 9.2.2.2 Feed Forward Capacitor CFF
        3. 9.2.2.3 Inductor Selection
        4. 9.2.2.4 Input Capacitor
        5. 9.2.2.5 Output Capacitor
      3. 9.2.3 Application Curves
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Third-Party Products Disclaimer
    2. 10.2 Documentation Support
      1. 10.2.1 Related Documentation
    3. 10.3 Receiving Notification of Documentation Updates
    4. 10.4 Support Resources
    5. 10.5 Trademarks
    6. 10.6 Electrostatic Discharge Caution
    7. 10.7 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

9.2.2.3 Inductor Selection

The TPS62A02-Q1 is designed for inductors with an effective inductance between 300nH and 1.2µH inductor with a switching frequency of typically 2.2MHz. Inductor selection follows these tradeoffs:

  • Larger inductance
    • Helps achieving a higher efficiency at output currents below 1A
    • Has a positive impact on current ripple
    • Results in lower output voltage ripple
    • Decreases transient response performance
  • Smaller inductance
    • Has a positive impact on inductor form factor at given maximum current capability
    • Is therefore more cost effective
    • Causes a larger inductor current ripple
    • Reduces efficiency
    • Causes larger negative inductor current in forced PWM mode at low or no output current
See Section 6.3 for details.

The inductor selection is affected by several conditions like input voltage range, output voltage, target output voltage ripple with specific output capacitance, and corresponding inductor current ripple. The inductor selection also has influence on the PWM-to-PFM transition point and efficiency. The inductor must be rated for the correct saturation current and average current. The DCR with the influence on converter efficiency must be as low as possible. Smaller inductor form factor typically leads to either higher DCR and lower current capabilities or to lower inductance. There are two main types of inductors available for use in buck converters:

  • Ferrite inductors
  • Iron powder inductors
Iron powder power inductors are very safe to use because the saturation of the magnetic material is soft. This means the inductance decrease resulting from the inductor current is relatively small and even. Even if iron powder inductors are operated close to the data sheet saturation current, there is low risk of damaging the TPS62A02-Q1 by overcurrent. The current rise is slow enough for the overcurrent protection of the TPS62A02-Q1 to still be effective. Contrary to iron powder inductors, a ferrite inductor can have a steep saturation curve. This steep saturation curve results in a much faster inductor current increase after the saturation is reached. There is a potential risk that the current rise is so quick that the overcurrent limit circuit inside the TPS62A02-Q1 cannot follow. Therefore, the application designer planning a saturation current reserve with ferrite inductors, which is large enough to cover the inductor tolerances and special cases like short-circuit and application start-up, is good practice.

Equation 3 calculates the maximum inductor current.

Equation 3. I L m a x = I O U T m a x + ∆ I L m a x 2
Equation 4. ∆ I L m a x = V O U T × 1 - V O U T V I N L m i n × 1 f S W

where

  • IL(max) is the maximum inductor current.
  • ΔIL(max) is the peak-to-peak inductor ripple current.
  • Lmin is the minimum inductance at the operating point.