Flickering problem with Arduino MEGA + TLC5940 + AD1408

As said in the title, I am controlling a multiplexed LED matrix with a combination of an ADG1408 as power switch and a TLC5940 as current sink, everything controlled by an Arduino MEGA.

The system works almost perfectly except for some LEDs that do not stay OFF but turn ON very dimly. I attach a video where the effect can be seen.

Flickering can be seen in the lower part of the PCB

I saw this effect for the first time when I was prototyping the ADG1408 on a breadboard, but it was only visible on the first LED. Now it is visible on two or three LEDs. I'm aware of this problem on the TLC5940 and I worked a lot on solving and alone it doesn't show any flicker.

The schematic of the system is as follows:


What could be the reason for the LEDs not staying off? I tried adding some pull-down resistors on the logic pins A0, A1, A2 and EN but it made no difference.

The voltage on the LEDs is 10V with a fixed current of 0.01A, the timing of the switching is 55ms so it should be on the safe-side of both ICs.

Touch here for the full post on the Arduino Apprentices tumblr

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