SLUSE50 November   2023 TPS92642-Q1

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  Internal Regulator
      2. 6.3.2  Buck Converter Switching Operation
      3. 6.3.3  Bootstrap Supply
      4. 6.3.4  Switching Frequency and Adaptive On-Time Control
      5. 6.3.5  Minimum On-Time, Off-Time, and Inductor Ripple
      6. 6.3.6  LED Current Regulation and Error Amplifier
      7. 6.3.7  Start-Up Sequence
      8. 6.3.8  Analog Dimming and Forced Continuous Conduction Mode
      9. 6.3.9  External PWM Dimming and Input Undervoltage Lockout (UVLO)
      10. 6.3.10 Pulse Duty Cycle Limit Circuit
      11. 6.3.11 Output Short and Open-Circuit Faults
      12. 6.3.12 Overcurrent Protection
      13. 6.3.13 Thermal Shutdown
      14. 6.3.14 Fault Indicator and Diagnostics Summary
    4. 6.4 Device Functional Modes
  8. 7 Application and Implementation
    1. 7.1 Application Information
      1. 7.1.1  Duty Cycle Considerations
      2. 7.1.2  Switching Frequency Selection
      3. 7.1.3  LED Current Programming
      4. 7.1.4  Inductor Selection
      5. 7.1.5  Output Capacitor Selection
      6. 7.1.6  Input Capacitor Selection
      7. 7.1.7  Bootstrap Capacitor Selection
      8. 7.1.8  Compensation Capacitor Selection
      9. 7.1.9  Input Dropout and Undervoltage Protection
      10. 7.1.10 Pulse Duty Cycle Limit Circuit
      11. 7.1.11 Protection Diodes
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
        1. 7.2.2.1 Calculating Duty Cycle
        2. 7.2.2.2 Calculating Minimum On-Time and Off-Time
        3. 7.2.2.3 Minimum Switching Frequency
        4. 7.2.2.4 LED Current Set Point
        5. 7.2.2.5 Inductor Selection
        6. 7.2.2.6 Output Capacitor Selection
        7. 7.2.2.7 Bootstrap Capacitor Selection
        8. 7.2.2.8 Compensation Capacitor Selection
        9. 7.2.2.9 VIN Dropout Protection and PWM Dimming
      3. 7.2.3 Application Curves
    3. 7.3 Power Supply Recommendations
    4. 7.4 Layout
      1. 7.4.1 Layout Guidelines
        1. 7.4.1.1 Compact Layout for EMI Reduction
          1. 7.4.1.1.1 Ground Plane
      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

Package Options

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

7.1.7 Bootstrap Capacitor Selection

The bootstrap capacitor biases the high-side gate driver during the high-side FET on-time. TI recommends that a 100-nF capacitor rated for 10 V or higher is used. The VBSTI(UV) threshold is designed to maintain proper high-side FET switching operation. If the CBST capacitor voltage drops below VBST(UV), then the device initiates a charging sequence, turning on the low-side FET before attempting to turn on the high-side FET. For a very low PWM frequency, the charging sequence is initiated on the rising edge of the PWM pulse. The duration of the low-side switch turn-on as a function of pulse width can be tuned by increasing the value of bootstrap capacitor, CBSTI, depending on the application.