SLIS178B October   2017  – January 2018 TPS92830-Q1

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Simplified Schematic
  4. 4 Revision History
  5. 5 Description (Continued)
  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 Timing Requirements
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Device Bias
        1. 8.3.1.1 Power-On-Reset (POR)
        2. 8.3.1.2 Current Reference (IREF)
        3. 8.3.1.3 Low-Current Fault Mode
      2. 8.3.2 Charge Pump
        1. 8.3.2.1 Charge Pump Architecture
      3. 8.3.3 Constant-Current Driving
        1. 8.3.3.1 High-Side Current Sense
        2. 8.3.3.2 High-Side Current Driving
        3. 8.3.3.3 Gate Overdrive Voltage Protection
        4. 8.3.3.4 High-Precision Current Regulation
        5. 8.3.3.5 Parallel MOSFET Driving
      4. 8.3.4 PWM Dimming
        1. 8.3.4.1 Supply Dimming
        2. 8.3.4.2 PWM Dimming by Input
        3. 8.3.4.3 Internal Precision PWM Generator
        4. 8.3.4.4 Full Duty-Cycle Switch
      5. 8.3.5 Analog Dimming
        1. 8.3.5.1 Analog Dimming Topology
        2. 8.3.5.2 Internal High-Precision Pullup Current Source
      6. 8.3.6 Output Current Derating
        1. 8.3.6.1 Output-Current Derating Topology
      7. 8.3.7 Diagnostics and Fault
        1. 8.3.7.1 LED Short-to-GND Detection
        2. 8.3.7.2 LED Short-to-GND Auto Retry
        3. 8.3.7.3 LED Open-Circuit Detection
        4. 8.3.7.4 LED Open-Circuit Auto Retry
        5. 8.3.7.5 Dropout-Mode Diagnostics
        6. 8.3.7.6 Overtemperature Protection
        7. 8.3.7.7 FAULT Bus Output With One-Fails–All-Fail
        8. 8.3.7.8 Fault Table
    4. 8.4 Device Functional Modes
      1. 8.4.1 Undervoltage Lockout, V(IN) < V(UVLO)
      2. 8.4.2 Normal Operation (V(IN) ≥ 4.5 V, V(IN) > V(LED) + 0.5 V)
      3. 8.4.3 Low-Voltage Dropout
      4. 8.4.4 Fault Mode (Fault Is Detected)
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Typical Application for Automotive Exterior Lighting With One-Fails–All-Fail
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curves
      2. 9.2.2 High-Precision Dual-Brightness PWM Generation
        1. 9.2.2.1 Dual-Brightness Application
        2. 9.2.2.2 Design Requirements
        3. 9.2.2.3 Detailed Design Procedure
        4. 9.2.2.4 Application Curve
      3. 9.2.3 Driving High-Current LEDs With Parallel MOSFETs
        1. 9.2.3.1 Application Curves
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Receiving Notification of Documentation Updates
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

8.3.5.1 Analog Dimming Topology

Voltage at the ICTRL pin, V(ICTRL), is used for analog dimming control. To set V(ICTRL), either a reference input voltage can be applied or a resistor between ICTRL and GND can be used.

When V(ICTRL) is greater than V(ICTRL_FULL), analog dimming is not enabled; thus the analog dimming ratio is at 100%.

When V(ICTRL) is between V(ICTRL_LIN_BOT) and V(ICTRL_LIN_TOP), the analog dimming ratio is directly proportional to V(ICTRL). The analog dimming ratio can be calculated using the following equation. V(ICTRL_LIN_BOT) and V(ICTRL_LIN_TOP) represent the ICTRL voltage boundaries of the linear region.

    Equation 7. TPS92830-Q1 Equation_05_SLIS178.gif

When VICTRL is between V(ICTRL_LIN_TOP) and V(ICTRL_FULL) or between V(ICTRL_LIN_BOT) and 0, analog dimming is in a transition region, and linearity is not assured. Thus it is not recommended to use ICTRL in these regions.

TPS92830-Q1 Analog_Dimming_Ratio_SLIS178.gifFigure 26. Analog Dimming Ratio