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LED Control on Pattern sequence mode

Natty Dale
Prodigy 225 points


Hi there,

When display mode is set to pattern sequence, An interesting effect happens that even with 1bit setting, when RED or BLUE LED is chosed, setting Green LED current to 0  leads to no display at all. But  the RED or BLUE LED is still set to a non-zero value, e.g. 274.

Why is that? How to fix this problem?

regards

Natty

  • 0
    TI__Expert 4500 points

    Hi Natty,

    Sorry for delay in my response, I was on extended vacation. In LED driver circuit (LightCrafter Driver Board Schematic, Page 5), if the LED current value is set to zero on the GUI, the current value increases greatly due to no load on DC-DC converter (TPS63020DSJ). A minimum value of '1' is recommended for all three LEDs.

    Regards,

    Divya

  • 0 in reply to Divya Reddy
    Intellectual 465 points

    Hi Divya,

    I was wondering the same thing -- why the green LED setting affects the red/blue LEDs as well. 

    I'm not sure if I fully understand the answer given here...  does this mean it's not a good idea to set the LED current to 0 in any case?  We were thinking to set all values to 0 to turn the LightCrafter "off" whenever it's not in use to minimize heat. 

    We tried displaying black, but it seems the light engine is still on and generating heat.  I haven't tried the curtain bit (0xA6) yet, but I imagine that'd work the same. 

  • 0 in reply to Pete Thompson
    TI__Expert 4500 points

    Hi Pete,

    We have measured the LED currents indirectly by passing the light through integrated sphere and connecting a detector to measure the value.

    Below are the measurements taken from one of the LightCrafter units, LED Current Set is the GUI setting, Detector current is measured value from the detector and 5.0v Current is the 5V input supply

    As you can see, the high current draw at a setting of '0' is causing LED driver anode voltage oscillations. It is highly recommended not to set the LED current value to '0'.

    Regards,

    Divya