Pramod:
Many times when you are expanding I/O there is also a need to for that I/O to have output drive characteristics that are more robust than can be achieved with the 8255. In these cases there is a way this done in a serial manner as suggested by IJAZ but at the same time get the higher rated drive capabilities. A manufacturer to look at for serial shift registers with special output characteristics is Allegro.

They make a whole series of parts and here is the block diagram for one of them that is a serial output called the UCN5841. The outputs on it are open collector and can sink up to 500 mA per output.



The full technical data for this part is at Allegro UCN5841.

You can also review a whole list of the power drivers from Allegro at www.allegromicro.com/selguide

Michael Karas