LED7708 flickering/flashing issue

[b_1]

Hi

We observe sudden changes and flickering especially at low level luminosity.

attached oscilloscope capture_1 is taken at one of green LED channels. During the dimming cycle, the ghost pattern causes momentary flashes in LED brightness.

again oscilloscope capture_2.PNG and oscilloscope capture_3.PNG are taken at one of green channels. In this case LOW side resistor of output driver value decreased; and noticed a noise at ON state. There is also a flicker in this case and we suppose the cause is the noise seen in oscilloscope capture_3.PNG.

The flickering and flashing mostly seen at low luminosity values.

Do you have and suggestion on fixing these?

our design is:

LED7708 : 10 channels active, and 8 LEDs on each channel. There are 4 LED7708s on the same board.

LED PN : osram LRTB GVTG

thanks,

Baris

[b_1 · Accepted solution]

SOLVED

C19 (parallel to Riseth resistor) marked as NC in the evaluation board schematics, was populated in our design. Removing this cap. solved the problem.