Can you think of only one way to do this? Think one or more cathode driver per LED in each pixel. Surely you can envision a way of driving a multi-led pixel with multiple cathode drivers, one or two at a time. Think duty cycle limits! Think BIG signs (10 Meters x 25 Meters) with 256 LED's per pixel! Think pixels the size of a silver dollar! After all, the O/P didn't specify the size or whether it was indoor or outdoor!



Maybe I could have made it more clear. If you have 1280 pixels with 4 LED's per pixel, you certainly know how you're going to drive each pixel. If you use pairs or quads of LED's in order to increase light output, you have a common source, in your common anode case, and you have one constant current sink per LED, which means four per pixel. YOU, the designer, get to decide, in advance, how they'll be driven. You know, as precisely as the components allow, how many are lit, since the choice was made before the device was built, and how much current will flow, and for how long. If you've no idea how much current will flow, somethings is wrong ... with YOU, and not with the circuit.

If, due to other constraints, you choose to drive two of the four LED's at a time, in order to limit the power dissipated in the LED's or in the current sink, you still have complete control, hence, foreknowledge of the amount of power. If you don't you've fallen asleep at the switch.

Of course, in such a case, you'd have 5120 LED's and 5120 drivers, or, if the cathode drivers are shared (common), there would be half or a quarter as many. If you common the cathode driver, however, you have to switch the anode source on and off in order to determine which is on. You can, in fact, share two cathode drivers on one single cathode, in order to limit the driver heating. This has all been done before. It's not a mystery.

RE