See the attached schematic fragment.
This question is more of a programming question. I have this setup on a board running on a 7.3728MHz crystal that also has PWM audio, with a 4KHz cutoff filter, and audio sampling will be output by PWM at 14.4KHz. So to limit the switching noise coupling to the audio signal, I was thinking of scanning the display as 5 phases (20% duty cycle) on a timer running at 14.4KHz/28.8KHz. I realize this is unnecessary, and the display could be scanned at <1KHz, but I am worried the transistor switching will be clearly audible in the audio output.
I am also worried that at 3.3v 10mA 20% duty cycle the LEDs might be a bit dim. I have no previous experience with these displays, although I do understand how to light up a few LEDs obviously. They all seem to have similar specs, and I was wondering if anyone played with those before, and if you think the above scheme will be fine.