Thank you for your answer! I don't know whether I fully understand the content. So I have another question..If I supply adequate current and resistors, is it okay to use LOW pin as GND?
I thought dot matrix uses LOW OUTPUT pin as GND and scanning purposes. Does dot matrix dont need GND?
Yes.That is the same as 5V-high drive transistor-LED-resistor - low drive transistor - GND.The transistors have an Rds (resistance drain to source) of around 25 ohm.If the LED have a Vf of ~2.5V, and you wanted say 15mA to flow thru the LED, then:(5V - 2.5V)/.015A = 167 ohm. Minus the 25 ohm of each resistor leaves 117 ohm current limit resistor needed.120 is standard value.(5V - 2.5V)/(25 ohm + 25 ohm + 120 ohm) = 14.7mA. Pretty darn close.
No. It does require a voltage between the anode and cathode drives. It just happens that usually that is provided by an effective ground. The thread you linked to has nothing to do with scanning matrices, you can just ignore it for this question. That thread is talking about using a ground as a semi-permanent power sink for a device that is constantly on for periods of time.