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
8.2.1.2.1 Inductor Selection

There are two main considerations when choosing an inductor; the inductor must not saturate, and the inductor current ripple must be small enough to achieve the desired output voltage ripple. Different saturation current rating specifications are followed by different manufacturers so attention must be given to details. Saturation current ratings are typically specified at 25°C. However, ratings at the maximum ambient temperature of application should be requested from the manufacturer. Shielded inductors radiate less noise and are preferred. The saturation current must be greater than the sum of the maximum load current, and the worst case average-to-peak inductor current. Equation 4 shows the worst case conditions

Equation 4. GUID-DCB2CC12-9C4F-47AF-9059-0441A7790195-low.gif
  • IRIPPLE - peak inductor current
  • IOUTMAX - maximum load current
  • VIN - minimum input voltage in application
  • L - min inductor value including worst case tolerances
  • f - minimum switching frequency
  • VOUT - output voltage
  • D - Duty Cycle for CCM Operation

As a result, the inductor should be selected according to the ISAT. A more conservative and recommended approach is to choose an inductor that has a saturation current rating greater than the maximum current limit. A saturation current rating of at least 2.5 A is recommended for most applications. See Table 7-2 for recommended inductance value for the different switching frequency ranges. The inductor’s resistance should be less than
300 mΩ for good efficiency.

See detailed information in Understanding Boost Power Stages in Switch Mode Power Supplies. Power Stage Designer™ Tool can be used for the boost calculation: http://www.ti.com/tool/powerstage-designer.