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
8.2.1.2.3 Output Capacitor Selection

The output capacitor reduces the high-frequency ripple current through the LED string. Various guidelines disclose how much high-frequency ripple current is acceptable in the LED string. Excessive ripple current in the LED string increases the RMS current in the LED string, and therefore the LED temperature also increases.

1. Calculate the total dynamic resistance of the LED string (RLED) using the LED manufacturer's data sheet.

2. Calculate the required impedance of the output capacitor (ZOUT) given the acceptable peak-to-peak ripple current through the LED string, ILED(ripple) × IL(ripple), is the peak-to-peak inductor ripple current as calculated previously in inductor selection.

3. Calculate the minimum effective output capacitance required.

4. Increase the output capacitance appropriately due to the derating effect of applied dc voltage.

See Equation 6, Equation 7, and Equation 8.

Equation 6. GUID-2B23A8B7-D5F2-4B4D-9243-22EFEDA13A08-low.gif
Equation 7. GUID-4DBC923C-D4DC-4D09-951F-44F04D096369-low.gif
Equation 8. GUID-F0938944-0337-46B6-95D6-66A2147F1EAD-low.gif

After the output capacitor is chosen, Equation 9 can be used to estimate the peak-to-peak ripple current through the LED string.

Equation 9. GUID-97E4ABC0-E3DC-45B1-AC79-99A6FDD7A5A6-low.gif

OSRAM SFH4715A IR LED is used here. The dynamic resistance of this LED is 0.29 ohm at 1.5-A forward current. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. In this design, a 10-µF, 35-V X7R ceramic capacitor is chosen, the part number is GRM32ER7YA106KA12L. The calculated ripple current of the LED is about 23.8 mA.
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