I had did some search for selection of seven segment displays for design....i.e. when to use common Cathode and when to use common anode....in another word what are the advantages that one will get if one is using common cathode displays over common anode and vice versa....but could not able to get satasficatory answers....
The choice between Common Cathode and Common Anode usually comes down to whether the LED driver, MCU pin, transistor, etc, can source or sink the required current to drive the LED.
If the LED driver can reliably source the current required, then a Common Cathode configuration is warranted.
However, if the LED driver must sink the current required, then a Common Anode configuration should be utilized.
The active signal level of the LED driver may also influence the choice, Common Cathode requires an Active High Signal and Common Anode requires an Active Low Signal.
MCUs not only have a per PIN current sinking or sourcing limit, but a device Vdd and Vss, current sinking and sourcing limit as well.
By carefully planning which pins will being sourcing current and which pins will being sinking current, the Maximum Limits of the device can be preserved.
When planning your design you may find it advantageous to sink current from a Common Anode LED, than source current to a Common Cathode LED.
BigDog