I really love building LED displays and have a decent understanding of multiplexing at this point. However, everything I've built is just binary, on or off, and I've been interested in building displays with LEDs with 2 or 4 bits of brightness depth, which I believe is most easily achieved with PWM.
I've looked at drivers like the TLC5955 and TLC5947 which seem to do the job. With 24 or 48 channels, that's enough to cover a "row" of what I want to create.
I'm just uncertain if it is possible to multiplex with a chip like this. They have an open drain, so I wonder if I just shared all the Cathodes for each row on the chip, then I could just do a refresh cycle where I drop the anodes for each row to low on an update, and keep the others high.
Best Answer
Yes, I think it should be possible. Going from the datasheet of the TLC5955, one of the mentioned applications is "LED video displays".
If I understand correctly, you plan to connect one channel/pin to a group of shared cathodes (-), which is a column in you matrix. A row in the matrix has shared anodes, and only one row should be on at the same time. If you then update the channel outputs each time you switch row is on, then that should work.
Also, the datasheet mentions a maximum current sinking capability of 31.9 mA. As long as a single LED doesn't exceed that value, and you ensure that only one row is active at all times, that should work too.