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

1.8 PWM Dimming

The PWM dimming can be achieved through the UDIM pin and SDIM pin. The UDIM pin can be driven with a PWM signal which controls the synchronous NFET operation. The brightness of the LEDs can be varied by modulating the duty cycle (DDIM) of the signal using a Schottky diode with anode connected to UDIM pin. The SDIM pin is controlled with an external shunt FET PWM dimming. Extremely high dimming range and linearly is achieved by shunt FET dimming operation with the SDIM and SDRV pin. When higher frequency and time resolution PWM dimming signal is applied to the SDIM pin, the SDRV pin provides an inverted signal of the same frequency and duty cycle that can be used to drive the gate of a shunt NFET directly across the LED load.