ZHCU740 April   2020

 

  1.    说明
  2.    资源
  3.    特性
  4.    应用
  5.    设计图像
  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 商标
    2. 4.2 Third-Party Products Disclaimer

1.5 LED Driver SDIM/UDIM Settings

There are 2 control signals that can be options to turn LEDs on and off – UDIM and SDIM. UDIM controls the synchronous NFET operation of the buck regulator and provides for a slower turn on of the LEDs. SDIM turns off/on shunt NFET that quickly shunts current from and to the LED providing for faster rise time. SDIM rise time is x5 faster than UDIM. SDIM fall time is x20 times faster than UDIM. LED load, as well as capacitor that is placed in parallel with the load, can influence rise/fall time of the current (current rise/fall time vs. capacitor is addressed in Section 2.5)

Each LED driver block has a connector that allows for flexibility of design in testing UDIM and SDIM operation. Current board is set up for SDIM operation.

Figure 6. UDIM/SDIM HeaderTIDA-080008 SDIM_UDIM.gif

Table 4. Default Jumpers

OPTIONS CONNECTOR SETTING OTHER REQUIREMENTS
SDIM (Default) Jumper together pin 5 and 6 Shunt NFET must be populated
UDIM Jumper together pin 4 and 3 Shunt NFET must be depopulated

NOTE

Warning: Make sure UDIM is driven to 0 V during power up, especially when main supply that drives LEDs is on. If UDIM is left floating, it will apply constant VLED voltage/current and might damage the LED, if LED is meant to be pulsed.