At 04:48 PM 2/4/02 +1300, you wrote:
> > 1)      Average LED current
>
>Which should not be under-estimated. Pulsing LEDs at high
>speed can cause instantaneous currents of amps - not good
>for a PIC pin. Better for a more suitable device to take that
>sort of punishment. Although the LEDs are receiving these
>pulses, we don't (and shouldn't) see them. It's our persistence
>of vision that makes them appear to have an even, average
>brightness and the display as whole to move smoothly

Yes, if they are run the way I recommend, the 8 source drivers will see the
ENTIRE
display current  with a 0.125 duty cycle. The PIC port pins (say that 3
times fast!) are
not capable of putting out that kind of current, they will go into
"constant current"
mode, at a somewhat unpredictable current well above the abs max data sheet
current. Neither good (repeatable) nor reliable design.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
9/11 United we Stand

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