Hi Eric,

I still have not managed to decide whether or not to "migrate" from muxed to non-muxed, so a mixture of mux and non-mux questions is in my mind.

As you know well, in a typical sign, we have LEDs, LED boards, LED drivers, mainboard, power supply and casing. Now assuming that the cost of casing, power supply and motherboard is rughly the same for both multiplexed and non multiplexed displays(unless of course there are things that I may have neglected) a rough approximation of the main cost issues will be:
(Some of items were omitted "from both sides" for the sake of simplicity ... Things like high side drivers from the mux side and instead, two layer epoxy-glass LED boards from the non-mux side.- In my former designs the 4-pin sipder LEDs gave me the opportunity to use single layer boards as LED board beacause each Spider LED containd a "jumper" inside it between the two "extra" leads. But in non-mux approach using two-lead cheap LEDs and the STs makes two layer epoxy-glass-FR4 boards inevitable which are of course [much] more expensive that one layer ones.)

mux: 8000 expensive LEDs, No ST2221s
non-mux: 8000 cheap LEDs, 500 "new" ST2221Cs: AN88161

Now the question is whether or not
8000 * (Price_{Expensive LED} - Price_{Cheap LED}) >> 500 * Price_{"new" ST2221C}
With
Price_{Expensive LED} = .18USD (toyolite.com-shipping not included)
Price_{Cheap LED} ~= .03USD (my approximation!)
Price_{"new" ST2221C} = .44USD (toyolite.com-shipping not included)
Well, seems easy to conclue, but the prices here are confusing:
Price_{Expensive LED} = 60 Tomans
Price_{Cheap LED} = 10 Tomans
Price_{"new" ST2221C} = 500 Tomans
Then
8000 * (Price_{EXPENSIVE LED} - Price_{CHEAP LED}) = 400,000 Tomans
And
500 * Price_{"new" ST2221C} = 250,000 Tomans
But Here the difference between the cost of 20,000 square cm of two layer LED board and one layer one is some 500,000 Tomans which completely covers everything! WHY?
Of course we still have these issues:
- easier synchronization in non-muxed
- No "aging" in non-muxed
- gluteus-friendly wiring in non-muxed

Plus one for turning off the display and for PWMing. Right?

Are those 648 STs -as I guess- solderred on the same board containing LEDs? Then does it not suggest using two layer epoxy-glass boards?

Adjusted for I_MAX of LED with R_EXT? ... Okay Iout = ( Pd – VDD.IDD) / ( # outputs.Vo.Duty )

Uhum ... Got any suggestions except using some 8 PC power supplys? Of course I read this:
_{Eric, 23/Jul/04}

While reading the I<OUT> vs. DutyCycle diagram of ST2221 (in a non-multiplexed display) is it Okay to consider the duty cycle to be some 90% provided that the needed time to hit strobe is short enough?

_{21/Feb/03, Eric
18/Mar/04, Eric}
Using the R_EXT...no...by PWMing right? Controlled by an "eye" or what?

_{15/Apr/03, Eric}
Do I have to use "heavy copper" boards? It seems that this "Vcc and Vled separated" is a suggestion for that original poster's approach, since the V_CC and V_LED of ST2221 series is the same ... I mean impossible to separate.

Best.