JAJSDL7D January   2016  – May 2021 TPS61194

PRODUCTION DATA  

  1. 1 特長
  2. 2 アプリケーション
  3. 3 概要
  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 (1) (1)
    6. 6.6  Internal LDO Electrical Characteristics
    7. 6.7  Protection Electrical Characteristics
    8. 6.8  Current Sinks Electrical Characteristics
    9. 6.9  PWM Brightness Control Electrical Characteristics
    10. 6.10 Boost and SEPIC Converter Characteristics
    11. 6.11 Logic Interface Characteristics
    12. 6.12 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 Integrated DC-DC Converter
      2. 7.3.2 Internal LDO
      3. 7.3.3 LED Current Sinks
        1. 7.3.3.1 Output Configuration
        2. 7.3.3.2 Current Setting
        3. 7.3.3.3 Brightness Control
      4. 7.3.4 Protection and Fault Detections
        1. 7.3.4.1 Adaptive DC-DC Voltage Control and Functionality of LED Fault Comparators
        2. 7.3.4.2 Overview of the Fault/Protection Schemes
    4. 7.4 Device Functional Modes
      1. 7.4.1 Device States
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Typical Application for 4 LED Strings
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Inductor Selection
          2. 8.2.1.2.2 Output Capacitor Selection
          3. 8.2.1.2.3 Input Capacitor Selection
          4. 8.2.1.2.4 LDO Output Capacitor
          5. 8.2.1.2.5 Diode
        3. 8.2.1.3 Application Curves
      2. 8.2.2 SEPIC Mode Application
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Inductor
          2. 8.2.2.2.2 Diode
          3. 8.2.2.2.3 Capacitor C1
        3. 8.2.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Receiving Notification of Documentation Updates
    4. 11.4 サポート・リソース
    5. 11.5 Trademarks
    6. 11.6 Electrostatic Discharge Caution
    7. 11.7 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

7.3.4.1 Adaptive DC-DC Voltage Control and Functionality of LED Fault Comparators

Adaptive voltage control function adjusts the DC-DC output voltage to the minimum sufficient voltage for proper LED current sink operation. The current sink with highest VF LED string is detected and DC-DC output voltage adjusted accordingly. DC-DC adaptive control voltage step size is defined by maximum voltage setting, VSTEP = (VOUT_MAX – VOUT_MIN) / 256. Periodic down pressure is applied to the target voltage to achieve better system efficiency.

Every LED current sink has 3 comparators for the adaptive DC-DC control and LED fault detections. Comparator outputs are filtered, filtering time is 1 µs.

GUID-8BED3F9A-D4E8-4DA8-B6C7-9DBB1C1DCE56-low.gifFigure 7-3 Comparators for Adaptive Voltage Control and LED Fault Detection

Figure 7-4 shows different cases which cause DC-DC voltage increase, decrease, or generate faults. In normal operation voltage at all the OUT# pins is between LOW_COMP and MID_COMP levels, and boost voltage stays constant. LOW_COMP level is the minimum for proper LED current sink operation, 1.1 × VSAT + 0.2 V (typical). MID_COMP level is 1.1 × VSAT + 1.2 V (typical) so typical headroom window is 1 V.

When voltage at all the OUT# pins increases above MID_COMP level, DC-DC voltage adapts downwards.

When voltage at any of the OUT# pins falls below LOW_COMP threshold, DC-DC voltage adapts upwards. In the condition where DC-DC voltage reaches the maximum and there are one or more outputs still below LOW_COMP level, an open LED fault is detected.

HIGH_COMP level, 6 V typical, is the threshold for shorted LED detection. When the voltage of one or more of the OUT# pins increases above HIGH_COMP level and at least one of the other outputs is within the normal headroom window, shorted LED fault is detected.

GUID-A9DFF8CF-807C-46BB-9A28-60145FD50768-low.gifFigure 7-4 Protection and DC-DC Voltage Adaptation Algorithms