ZHCSLC6B May   2020  – January 2022 TPS92200

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  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
    6. 6.6 Timing Requirements
    7.     Switching Characteristics
    8. 6.7 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 Peak-Current-Mode PWM Control
      2. 7.3.2 Setting LED Current
      3. 7.3.3 Internal Soft Start
      4. 7.3.4 Input Undervoltage Lockout
      5. 7.3.5 Bootstrap Regulator
      6. 7.3.6 Maximum Duty Cycle
      7. 7.3.7 Overcurrent Protection
        1. 7.3.7.1 High-Side MOSFET Overcurrent Protection
        2. 7.3.7.2 Low-Side MOSFET Sourcing Overcurrent Protection
        3. 7.3.7.3 Low-Side MOSFET Sinking Overcurrent Protection
      8. 7.3.8 Fault Protection
        1. 7.3.8.1 LED Open-Load Protection
        2. 7.3.8.2 LED+ and LED– Short Circuit Protection
        3. 7.3.8.3 LED+ Short Circuit to GND Protection
        4. 7.3.8.4 Sense-Resistor Open-Load Protection
        5. 7.3.8.5 Sense Resistor Short Circuit-to-GND Protection
        6. 7.3.8.6 Overvoltage Protection
        7. 7.3.8.7 Thermal Shutdown
    4. 7.4 Device Functional Modes
      1. 7.4.1 Enable and Disable the Device
      2. 7.4.2 TPS92200D1 PWM Dimming
      3. 7.4.3 TPS92200D1 Analog Dimming
      4. 7.4.4 TPS92200D2 Analog Dimming
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 TPS92200D1 12-V Input, 1.5-A, 2-Piece IR LED Driver With Analog Dimming
        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 Input Capacitor Selection
          3. 8.2.1.2.3 Output Capacitor Selection
            1. 8.2.1.2.3.1 Sense Resistor Selection
              1. 8.2.1.2.3.1.1 Other External Components Selection
        3. 8.2.1.3 Application Curves
      2. 8.2.2 TPS92200D1 24-V Input, 1-A, 6-Piece WLED Driver With PWM Dimming
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Inductor Selection
          2. 8.2.2.2.2 Input Capacitor Selection
          3. 8.2.2.2.3 Output Capacitor Selection
            1. 8.2.2.2.3.1 Sense Resistor Selection
              1. 8.2.2.2.3.1.1 Other External Components Selection
        3. 8.2.2.3 Application Curves
      3. 8.2.3 5-V Input, 1-A, 1-Piece IR LED Driver With TPS92200D2
        1. 8.2.3.1 Design Requirements
        2. 8.2.3.2 Detailed Design Procedure
          1. 8.2.3.2.1 Inductor Selection
          2. 8.2.3.2.2 Input Capacitor Selection
          3. 8.2.3.2.3 Output Capacitor Selection
            1. 8.2.3.2.3.1 Sense Resistor Selection
              1. 8.2.3.2.3.1.1 Other External Components Selection
        3. 8.2.3.3 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 接收文档更新通知
    2. 11.2 支持资源
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 术语表
  12. 12Mechanical, Packaging, and Orderable Information
8.2.1.2.1 Inductor Selection

Use Equation 2 to calculate the recommended value of the output inductor L.

Equation 2. GUID-C7FEF26C-856F-46BD-9B7F-BC6827C28430-low.gif

where

  • KIND is a coefficient that represents the amount of inductor ripple current relative to the maximum LED current.
  • ILED is the maximum LED current.
  • VOUT is the sum of the voltage across the LED load and the voltage across the sense resistor.

In general, the value of KIND is suggested between 0.2 and 0.4. For the application that can tolerate higher LED current ripple or use larger output capacitors, one can choose 0.4 for KIND, otherwise, smaller KIND like 0.2 can be chosen to get smaller LED current ripple.

With the chosen inductor value, the user can calculate the actual inductor current ripple using Equation 3.

Equation 3. GUID-53F3E638-1DB7-4457-9679-4E4495C669F6-low.gif

For TPS92200, TI suggests that the inductor current ripple be larger than 300 mA to assure loop stability. If the calculated inductor current ripple is less than 300 mA, TI suggests a smaller inductor.

The inductor RMS current and saturation-current ratings must be greater than those seen in the application. These ratings ensure that the inductor does not overheat or saturate. During power up, transient conditions, or fault conditions, the inductor current can exceed its normal operating current. For this reason, the most conservative approach is to specify an inductor with a saturation current rating equal to or greater than the converter current limit. This action is not always possible due to application size limitations. The peak-inductor-current and RMS current equations are shown in Equation 4 and Equation 5.

Equation 4. GUID-E22FDE94-1C96-4684-B6A1-6EA10FEA1BDE-low.gif
Equation 5. GUID-CF99688D-27CB-44B4-83D0-38C7F2CDFF16-low.gif

In this design, VIN(max) = 13.2 V, VOUT = 3.6 V, ILED = 1.5 A, choose KIND = 0.3, the calculated inductance is 5.8-µH. A 4.7-µH inductor is chosen. With this inductor, the ripple, peak, and RMS currents of the inductor are 0.56 A, 1.78 A and 1.51 A respectively. The chosen inductor has ample margin.
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