Erik, I know you are an expert on LED matrices. Do you always use non-multiplexed designs?

almost, I have one small sign that is multiplexed and the capability limitations resulting from that fact makes every delivery to a customer that want anything more than 'just plain' be a look-alike non-multiplexed version.

YES, You CAN multiplex, but you WILL be restricted in what you can do with things like color, scroll, intensity control, and more.

Were I to do featureless static monocolor signs, I MIGHT look into MPX, but, again, whwre are the savings. With multiplex you get a much more complex PCB (not an excuse), more EMI (valid excuse) and - last I checked - higher cost.

Also, the cost of the actual LED goes up when you multiplex, since it needs to withstand n times the current it would get in non-multiplexed.

the ST2221A is so cheap that you have to really do 'magic' to get a worthwhile savings out of multiplexing (everything has to be dimensioned for n times the current).

One issue, not to be ignored, is the tremendous amount of EMI a multiplexed sign generates.

I, personally, think most of the multiplexing is a holdover from the days when ICs actually cost money. Today when they are a dime, the story is different.

Erik