SNVSCN8A September   2025  – October 2025 TPS923610 , TPS923611 , TPS923612

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
    6. 6.6 Typical Characteristics
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Enable and Start-up
      2. 7.3.2 Under-Voltage Lockout (UVLO)
      3. 7.3.3 Shutdown
      4. 7.3.4 Boost Control Operation
      5. 7.3.5 Switching Peak Current Limit
      6. 7.3.6 Over-Voltage Protection
      7. 7.3.7 Output Current Setting
      8. 7.3.8 Output Current PWM Controlled Analog Dimming
      9. 7.3.9 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Normal Operation Mode
      2. 7.4.2 Over-Voltage Protection Mode
      3. 7.4.3 Shutdown Mode
  9. 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 LED Current Set Resistor
        2. 8.2.2.2 Inductor Selection
        3. 8.2.2.3 Output Capacitor Selection
        4. 8.2.2.4 Thermal Considerations
    3. 8.3 Power Supply Recommendations
    4. 8.4 Application Curves
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Device Support
    2. 9.2 Receiving Notification of Documentation Updates
    3. 9.3 Support Resources
    4. 9.4 Trademarks
    5. 9.5 Electrostatic Discharge Caution
    6. 9.6 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

8.2.2.2 Inductor Selection

Inductor selection impacts power efficiency, steady-state operation, transient response and loop stability. These factors make inductor selction the most important component in power regulator design. There are three important inductor specifications, inductor value, DC resistance and saturation current. Considering inductor value alone is not enough. The inductor value determines the inductor ripple current. Choose an inductor that can handle the necessary peak current without saturating and optimize light load efficiency when using dimming. In a boost regulator, the input DC current can be calculated as

Equation 4. I L ( D C ) = V O U T × I O U T V I N × η

where

  • VOUT = boost output voltage
  • IOUT = boost output current
  • VIN = boost input voltage
  • η = power conversion efficiency

The inductor current peak to peak ripple can be calculated as

Equation 5. Δ I L ( P - P ) = 1 L × 1 V O U T - V I N + 1 V I N × F S

where

  • ΔIL(PP) = inductor peak-to-peak ripple
  • L = inductor value
  • FS = boost switching frequency
  • VOUT = boost output voltage
  • VIN = boost input voltage

Therefore, the peak current IL(P) seen by the inductor is calculated with

Equation 6. I L ( P ) = I L ( D C ) + Δ I L ( P - P ) 2

Also, the valley current IL(V) seen by the inductor is calculated with

Equation 7. I L ( V ) = I L ( D C ) - Δ I L ( P - P ) 2

Inductor values can have ±20% tolerance with no current bias. When the inductor current approaches saturation level, inductance can decrease 20% to 35% from the 0A value depending on how the inductor vendor defines saturation current. When using an inductor with a smaller inductance value with relative light load, the inductor current ramps down to below zero before the end of each switching cycle due to forced continuous condition mode (FCCM), which reduces light load efficiency. Large inductance value provides much more output current and higher conversion efficiency. Thus, choose a sufficiently large inductor that that maintains a non-negative valley current under light-load conditions helps optimize efficiency.

For these reasons, a 10μH inductor is recommended based on input voltage, output voltage and output current condition of this application, to maintain non-negative current in most of load range by PWM controlled analog dimming.