I am interested in utilizing a PIC Microcontroller in one of my projects when I realized in the datasheet pinout. that it requires 2 voltage sources. So my question is why do some Microcontrollers require 2 voltage sources ass opposed to one?

 

This one requires one source, 5V, but needs you to connect that source to two sets of pins on the package. Internally, the designers decided to power the internal power busses from both ends. Bigger packages like PLCC68 or 100 will have their Vdd / Vss applies to several sets of pins for the same reason i.e. Better internal power distribution with smaller geometries. This is not to be confused with the Add/AVss found on some parts to power the internal analog sections.

 

This one requires one source, 5V, but needs you to connect that source to two sets of pins on the package. Internally, the designers decided to power the internal power busses from both ends. Bigger packages like PLCC68 or 100 will have their Vdd / Vss applies to several sets of pins for the same reason i.e. Better internal power distribution with smaller geometries. This is not to be confused with the Add/AVss found on some parts to power the internal analog sections.

Thanks for the quick response!

 

Thanks for the quick response!

You're welcome. While we are on the subject, be sure to add your power supply decoupling to both sets of pins. 1uF tantalum || .1uF ceramic at each set of power pins is a good starting point.

 

You're welcome. While we are on the subject, be sure to add your power supply decoupling to both sets of pins. 1uF tantalum || .1uF ceramic at each set of power pins is a good starting point.

Generally you only need one tantalum somewhere on the V+ line to ground.
You do need the ceramic directly at each power pin to ground with short leads.