Pathu:
Arduino Nano 3.0 ATMega328 ?
To get the three outputs you want on an AVR processor you will have to use three timers. The m328 processor has three timers. Which means you will have to give up millis / micros; you will not be able to use a timer for anything else.
Is that going to work for your application?
at 1 MHz
With a processor running at 16 MHz that gives you 16 steps.
Is that going to work for your application?