why there are two Vdd and Vss in pic16f877a ?

[engr_najam]

Can any body please explain the need of two Vdd and Vss on PIC16f877A and others, even if they are internally then what is the need of them then ??

 

[JoKKeR]

Probably because of size. Some DIP packages got 1 VSS and 1 VDD, but SOIC package got 2 both.

Iv seen in a data sheet ... that 1 pin sink current max is 25 mA but whole pic pins got sum of 200 mA. This logic sequence continues: Cant sink 200 mA from only 1 small VDD pin (SOIC package).

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My questions for PROs


How to power pic internal RTCC. If main power source is AC adapter.
How to connect a battery and how to use it when it is only needed.

Thank you !