I am thinking how to reduce the EMI noise of the large LED indicators driven by tlc5947. This chip has digital outputs that limit/regulate current through light emitting diodes by switching on and off. The internal oscillator runs at about 4 MHZ and it looks like quite a powerful circuitry, 12 V, 600 mA for all assembly.
One of the ideas coming to mind is to use ferrite beads sequentially with LED diodes in the output. The concerns against are that be these inductors, they may generate the voltage spikes when current is turned off. From the other side, some sources say that ferrites do no accumulate as much energy as a coil of relay that would absolutely require a diode.
There are 24 channels per chip, and there are multiple chips, so this means lots of ferrite beads. But they are quite small and rather cheap so probably can be mounted if the bead is enough. With such amount of components, adding extra capacitors, resistors per every channel looks like no fun.
Could anybody with the knowledge say how good is the idea to put ferrite beads on the digital PWM output of the LED control chip running at 4 MHZ? I understand that the best would be to build the two prototypes and measure with near field probe (that would show the difference between the versions but not 'good enough' - 'not good enough') or at least just directly the waveform. There is a job and cost to build however. Maybe there is some generic knowledge on how good the idea is.
The goal is just to reduce the possible EMI noise. The indicators work very well, they do not even thing to flicker or the like.
P.S. Answers of the kind I should not be designing the circuit just because I am asking this question are out of scope.