SLVSCK5C September   2014  – January 2020 TPS92638-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Typical Application Schematic
  5. 5 Revision History
  6. 6 Pin Configuration and Functions
    1.     Pin Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Switching Characteristics
    7. 7.7 Typical Characteristics
  8. 8 Parameter Measurement Information
  9. 9 Detailed Description
    1. 9.1 Overview
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 LED Current Setting
      2. 9.3.2 PWM Control
      3. 9.3.3 Fault Diagnostics
        1. 9.3.3.1 Open-Load Detection
      4. 9.3.4 Thermal Foldback
    4. 9.4 Device Functional Modes
  10. 10Application and Implementation
    1. 10.1 Application Information
    2. 10.2 Typical Applications
      1. 10.2.1 PWM Dimming by Bank
        1. 10.2.1.1 Design Requirements
        2. 10.2.1.2 Detailed Design Procedure
        3. 10.2.1.3 Application Performance Plots
      2. 10.2.2 Two Brightness Levels for TAIL and STOP Lights
        1. 10.2.2.1 Design Requirements
        2. 10.2.2.2 Detailed Design Procedure
      3. 10.2.3 PWM Dimming by Modulated Supply
        1. 10.2.3.1 Design Requirements
        2. 10.2.3.2 Design Procedure
      4. 10.2.4 Driving LEDs From a Single Device With Channels in Parallel
        1. 10.2.4.1 Design Requirements
        2. 10.2.4.2 Design Procedure
      5. 10.2.5 Driving LEDs From Multiple Devices With Channels in Parallel
        1. 10.2.5.1 Design Requirements
        2. 10.2.5.2 Design Procedure
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1 Layout Guidelines
    2. 12.2 Layout Example
    3. 12.3 Thermal Information
  13. 13Device and Documentation Support
    1. 13.1 Trademarks
    2. 13.2 Electrostatic Discharge Caution
    3. 13.3 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

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

10.2.3 PWM Dimming by Modulated Supply

The TPS92638-Q1 device supports PWM dimming from the supply as depicted below. A high-side switch in the body control module (BCM) usually implements supply dimming. Due to the nature of the high-side switch, TPS92638-Q1 supply voltage is not strongly pulled down to ground, but depends on the decoupling capacitor and total current consumption. The TPS92638-Q1 device keeps the output current constant as long as supply voltage is adequate to overcome the LED forward voltage and dropout voltage.

When supply voltage drops too low to drive LEDs, the device shuts down the output channels on open-load detection. Therefore, TI recommends ensuring channel shutdown using the PWM or EN inputs. Thus a resistor string of R1 and R2 is recommended to ensure the lowest divided voltage is lower than PWM threshold.

TPS92638-Q1 PWM_dimming_supply_slvsck5.gifFigure 42. Schematic for PWM Dimming by Modulated Supply