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
7.2.1.2.7 Output Capacitor Selection

The output capacitor is critical for minimizing high-frequency current ripple in the LED string. Excessive ripple increases the RMS current within the LEDs, leading to elevated junction temperatures and reduced lifespan. To ensure optimal performance, follow these design steps:

1. Determine LED Dynamic Resistance RLED:Obtain the total dynamic resistance of the LED string from the LED manufacturer's datasheet.

2. Define Target Ripple Current : Determine the maximum acceptable peak-to-peak ripple current through the LED string ILED_RIP.

3. Calculate Required Impedance ZCOUT: Using the target ILED_RIP and the peak-to-peak inductor ripple current IL_RIP, calculate the required output capacitor impedance.

given the acceptable peak-to-peak ripple current through the LED string, ILED_RIP . IL_RIP is the peak-to-peak inductor ripple currentIL_MAX is the inductor maximum current as calculated with the selected inductor.

4. Calculate Minimum Capacitance COUT_MIN:Derive the minimum effective output capacitance required to meet the impedance target.

5. Account for DC Bias Derating: Increase the nominal capacitance value to compensate for the DC bias derating effect common in ceramic capacitors at the operating voltage.

Refer Equation 20, Equation 21, and Equation 22 for detailed calculation formulas.

Equation 20. R L E D = ∆ V F ∆ I F × # o f L E D s
Equation 21. Z C O U T = R L E D × I L E D _ R I P I L _ R I P - I L E D _ R I P
Equation 22. C O U T = 1 2 π × F S W × K D R × Z C O U T

Once the output capacitor is chosen, Equation 23 can be used to estimate the peak-to-peak ripple current through the LED string.

Equation 23. I L E D _ R I P = Z C O U T × I L _ R I P Z C O U T + R L E D

CREE WLED is used here. The dynamic resistance of the LED is 0.67Ω at 3A forward current. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of the low ESR and small temperature coefficients. In this design, a 3.3µF, 100V X7R ceramic capacitor and a 0.1µF, 100V X7R ceramic capacitor are chosen. The calculated ripple current of the LED is about 100mA.