SMPS rating calculation help

[anroop]

I have formulated a circuit. it uses 6 stepper motors (12v, 1.1A each) and IC with 5v input. but only two motors run simultaneously. what rating of SMPS should I go?

1) 12v with 2A
or
2) 12v with 3A

 

[Harald Kapp]

Obviously 2 motors will require 2*1.1A=2.2A which is more than the 12V/2A supply can deliver.
So 12V/3A is the power supply of your choice plus it leaves some headroom for current spikes.