TIDUEW9 April   2020

 

  1.    Description
  2.    Resources
  3.    Features
  4.    Applications
  5.    Design Images
  6. 1System Overview
    1. 1.1 Key System Specifications
    2. 1.2 Block Diagram
    3. 1.3 Top Side Pump
    4. 1.4 LED Driver Input Signals
    5. 1.5 LED Driver SDIM/UDIM Settings
    6. 1.6 TPS92641 Board Description
    7. 1.7 Setting the LED Current and Analog Dimming
    8. 1.8 PWM Dimming
  7. 2LED Driver Key Parameters
    1. 2.1 Enable and Disable Delay
    2. 2.2 Rise and Fall Time
    3. 2.3 Ripple
    4. 2.4 Performance Parameters
    5. 2.5 LED Load Capacitor for Rise/Fall Time
    6. 2.6 LED Load Capacitor And Audible Noise
      1. 2.6.1 Layout Considerations
      2. 2.6.2 Electrolytic capacitor considerations
      3. 2.6.3 Standoff Capacitors
    7. 2.7 LED Driver Calculator Tool
  8. 3Layout
  9. 4Related Documentation
    1. 4.1 Trademarks
    2. 4.2 Third-Party Products Disclaimer

2.2 Rise and Fall Time

Rise and fall times are how long it takes the light output to go from 10% to 90% and vice versa. The desired waveform should closely resemble a square wave as much as possible. The faster the time, the better the driver will perform. Keep in mind that the higher the rise time, the less margin one will have for the enable/delay. The fall time should be the same or better than the rise time. Potential issues from not having a fast rise times are ramp smoothness, PWM artifacts, CCA accuracy and dither performance.