SLVSI14A March   2026  – September 2026 TPS922152

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 Adaptive Off-Time Mode
      2. 6.3.2 Setting LED Current
      3. 6.3.3 VCC UVLO & Clamping
      4. 6.3.4 Dimming Mode
        1. 6.3.4.1 PWM Dimming
        2. 6.3.4.2 Analog Dimming
        3. 6.3.4.3 External Shunt Dimming
      5. 6.3.5 Fault Protection
  8. 7 Application and Implementation
    1. 7.1 Application Information
    2. 7.2 Typical Application
      1. 7.2.1 TPS922152 60V Input Bus, 5A Output, 16-piece WLED With Analog and PWM Dimming
        1. 7.2.1.1 Design Requirements
        2. 7.2.1.2 Detailed Design Procedure
          1. 7.2.1.2.1 Inductor Selection
          2. 7.2.1.2.2 MOSFET Selection
          3. 7.2.1.2.3 Diode Selection
          4. 7.2.1.2.4 MOSFET Selection
          5. 7.2.1.2.5 Diode Selection
          6. 7.2.1.2.6 Input Capacitor Selection
          7. 7.2.1.2.7 Output Capacitor Selection
          8. 7.2.1.2.8 Sense Resistor Selection
          9. 7.2.1.2.9 Other External Components Selection
        3. 7.2.1.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
      2. 7.4.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Receiving Notification of Documentation Updates
    2. 8.2 Support Resources
    3. 8.3 Trademarks
    4. 8.4 Electrostatic Discharge Caution
    5. 8.5 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information
7.2.1.2.1 Inductor Selection

For this design, the input bus voltage is a 60V rail with 10% variation. The output is 16 white LEDs in series and the inductor current ripple by requirement is less than 60% of maximum inductor current. To ensure compliance, the low-side FET current limit must not be exceeded during full-load operation. Specifically, peak current of inductor must be lower than the current limit. Additionally, the ripple current should be optimized to maintain reasonable inductor core and copper losses. After determining the target ripple current, use Equation 7 to calculate the recommended value of the switching inductor LSW.

Equation 7. L S W = V L E D × V B U S _ M A X - V L E D K I N D × I L E D _ M A X × F S W × V B U S _ M A X

where

  • KIND is a coefficient that represents the ratio of inductor ripple current to the maximum inductor current.
  • ILED_MAX is the maximum LED current.
  • FSW is the switching frequency.
  • VBUS_MAX is the maximum input bus voltage.
  • VLED is the sum of the voltage across LED load.

With the chosen inductor value, the user can calculate the actual inductor current ripple using Equation 8.

Equation 8. I L _ R I P = V L E D × V B U S _ M A X - V L E D L S W × F S W × V B U S _ M A X

To ensure reliable operation, the inductor's rated RMS current IL_RMS and saturation current IL_SAT must meet or exceed the maximum current levels defined by the system requirements. This prevents inductor overheating and magnetic saturation. During power-up, transient events, or fault conditions, the inductor current may surge beyond normal operating levels and approach the converter's current limit. To account for these surges, it is recommended to select an inductor with a saturation current IL_SAT equal to or greater than the converter's current limit. The equations for peak inductor current IL_PEAK and RMS current IL_RMS are provided in Equation 9 and Equation 10, respectively.

Equation 9. I L _ P E A K = I L _ M A X + I L _ R I P 2
Equation 10. I L _ R M S = I L _ M A X 2 + I L _ R I P 2 12

In this design, VBUS_MAX = 66V, VLED = 48V, ILED = 5A, FSW = 400kHz, select KIND = 0.6, the calculated switching inductance is 10.9µH. Select the closest standard 10µH ferrite inductor with an IL_RMS of 9.4A and an IL_SAT of 12.7A. A 10µH inductor is chosen. With this inductor, the ripple, peak, and rms currents of the inductor are 3.2A, 6.6A, and 5A, respectively.