SLUSCV5 May   2022 TPS92643-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and 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 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  Internal Regulator
      2. 7.3.2  Buck Converter Switching Operation
      3. 7.3.3  Bootstrap Supply
      4. 7.3.4  Switching Frequency and Adaptive On-Time Control
      5. 7.3.5  Minimum On-Time, Off-Time, and Inductor Ripple
      6. 7.3.6  LED Current Regulation and Error Amplifier
      7. 7.3.7  Start-Up Sequence
      8. 7.3.8  Analog Dimming and Forced Continuous Conduction Mode
      9. 7.3.9  External PWM Dimming and Input Undervoltage Lockout (UVLO)
      10. 7.3.10 Analog Pulse Width Modulator Circuit
      11. 7.3.11 Output Short and Open-Circuit Faults
      12. 7.3.12 Overcurrent Protection
      13. 7.3.13 Thermal Shutdown
      14. 7.3.14 Fault Indicator and Diagnostics Summary
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1  Duty Cycle Considerations
      2. 8.1.2  Switching Frequency Selection
      3. 8.1.3  LED Current Programming
      4. 8.1.4  Inductor Selection
      5. 8.1.5  Output Capacitor Selection
      6. 8.1.6  Input Capacitor Selection
      7. 8.1.7  Bootstrap Capacitor Selection
      8. 8.1.8  Bootstrap Resistor Selection
      9. 8.1.9  Compensation Capacitor Selection
      10. 8.1.10 Input Dropout and Undervoltage Protection
      11. 8.1.11 APWM Input and Thermal Protection
      12. 8.1.12 Protection Diodes
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1  Calculating Duty Cycle
        2. 8.2.2.2  Calculating Minimum On-Time and Off-Time
        3. 8.2.2.3  Minimum Switching Frequency
        4. 8.2.2.4  LED Current Set Point
        5. 8.2.2.5  Inductor Selection
        6. 8.2.2.6  Output Capacitor Selection
        7. 8.2.2.7  Bootstrap Capacitor Selection
        8. 8.2.2.8  Bootstrap Resistor Selection
        9. 8.2.2.9  Compensation Capacitor Selection
        10. 8.2.2.10 VIN Dropout Protection and PWM Dimming
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Compact Layout for EMI Reduction
        1. 10.1.1.1 Ground Plane
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Support Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.1.4 Inductor Selection

The inductor is sized to meet the ripple specification at maximum operating duty cycle. TI recommends a minimum sensed peak-to-peak voltage ripple (ΔV(CSP-CSN)) of 8 mV to ensure periodic switching operation under.

Equation 16. ∆V(CSP-CSN)=∆iL×RCS

Use Equation 17 to calculate the inductor value.

Equation 17. L = V I N , M I N - V C S N , M A X ∆ i L × f S W × V C S N , M A X V I N , M I N

The maximum inductor current ripple occurs at 50% duty cycle. Use Equation 18 to calculate the maximum peak-to-peak inductor current ripple, ΔiL(MAX).

Equation 18. ∆iL(MAX)=VIN(TYP)4×L×fSW

Use Equation 19 and Equation 20 to calculate the RMS and peak currents through the inductor. Make sure that the inductor is rated to handle these currents.

Equation 19. iLRMS=ILEDMAX2+ΔIL(MAX)212
Equation 20. iLPK=ILEDMAX+ΔiLMAX2