ZHCSBB4B July   2013  – June 2017 TPS61197

PRODUCTION DATA.  

  1. 1 特性
  2. 2 应用范围
  3. 3 说明
    1.     Device Images
      1.      简化原理图
  4. 4 修订历史记录
  5. 5 Pin Configuration and Functions
    1.     Pin 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 Switching Characteristics
    7. 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 Supply Voltage
      2. 7.3.2 Boost Controller
      3. 7.3.3 Switching Frequency
      4. 7.3.4 Enable and Undervoltage Lockout
      5. 7.3.5 Power-Up Sequencing and Soft Start-up
      6. 7.3.6 Current Regulation
      7. 7.3.7 PWM Dimming
      8. 7.3.8 Indication for Fault Conditions
    4. 7.4 Device Functional Modes
      1. 7.4.1 Protections
        1. 7.4.1.1 Switch Current Limit Protection Using the ISNS Pin
        2. 7.4.1.2 LED Open Protection
        3. 7.4.1.3 Schottky Diode Open Protection
        4. 7.4.1.4 Schottky Diode Short Protection
        5. 7.4.1.5 IFB Overvoltage Protection
        6. 7.4.1.6 Output Overvoltage Protection Using the OVP Pin
        7. 7.4.1.7 IFB Short-to-Ground Protection
        8. 7.4.1.8 Thermal Shutdown
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Applications
      1. 8.2.1 Simple Boost Converter
        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
          3. 8.2.1.2.3 Schottky Diode
          4. 8.2.1.2.4 Switch MOSFET and Gate Driver Resistor
          5. 8.2.1.2.5 Current Sense and Current Sense Filtering
          6. 8.2.1.2.6 Loop Consideration
        3. 8.2.1.3 Application Curves
      2. 8.2.2 PWM Dimming Controlled by Boost Converter
      3. 8.2.3 High Boost Ratio Application
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11器件和文档支持
    1. 11.1 接收文档更新通知
    2. 11.2 社区资源
    3. 11.3 商标
    4. 11.4 静电放电警告
    5. 11.5 Glossary
  12. 12机械、封装和可订购信息

封装选项

机械数据 (封装 | 引脚)
散热焊盘机械数据 (封装 | 引脚)
订购信息

7.3.7 PWM Dimming

LED brightness dimming is set by applying an external PWM signal of 90 Hz to 22 kHz to the PWM pin. Varying the PWM duty cycle from 0% to 100% adjusts the LED from minimum to maximum brightness, respectively. The recommended minimum on-time of the LED string is 10 µs. Thus, the TPS61197 has a minimum dimming ratio of 5000:1 at 200 Hz.

When the PWM voltage is pulled low during dimming off, the TPS61197 turns off the LED string and keeps the boost converter running in pulse frequency modulation (PFM) mode. In PFM mode, the output voltage is kept at a level which is a little bit lower than that when the PWM voltage is high. Thus, the TPS61197 limits the output ripple due to the load transient that occurs during PWM dimming.

When the PWM voltages are pulled low for more than 20 ms, to avoid the REF pin voltage dropping due to the leakage current, the voltage of the REF pin is held by an internal reference voltage, which is a little bit lower than the REF pin voltage in normal dimming operation. Thus, the output voltage is kept unchanged during the long dimming off time.

Because the output voltage in long-time dimming off status is almost the same as the normal voltage for turning the LED on, the TPS61197 turns on the LED very fast without any flicker when recovering from long-time dimming off to normal dimming operation.