Thanks for that...well I tried it (basically supplying a PIC off 3.3v) ...it all works, but alas, the LEDS aren't quite bright enough.

A bit of experimentation suggests a supply voltage of about 3.6V would be best ...but I need the regulator to be a SOT23-3 package& they don't seem to exist in 3.6V voltages.

My immediate thoughts re a kludge is to use a 4V regulator but use PWM to feed the LED 'common cathodes ' with 0V only 90% of the time ....which is effectively a voltage of 3.6V across the LEDs?? (yeah I know, it's not really it's still 4V across the LEDs ...albeit for only 90% of the time ....but I'm thinking that at least the LEDs, will have 10% 'downtime' to cool off from the extra current through 'em)

Do-able?