The LCD requires 3 mA for logic and 120 mA for the backlight.
The max the PIC can handle is 250 mA.
If I get this correctly, the circuit would feed through the LM78L05 producing a regulated 5v. Then I would connect a LED with a forward voltage of 1.7 in series to the PIC, which would produce the 3.3 needed to power the PIC.
The PIC is being used to run a PWM circuit to a MOSFET, external crystal for time and an LCD. Does current have any affect on the I/O ports or on a MOSFET?
What size wall wart should I use?
Feed the PIC the required voltage (3.3V) and it will only draw the current it needs. The amount of current it will draw depends on it's clock speed, how many peripherals are enabled, how much current it's IO pins is sourcing, etc. There is a chart in the datasheet which show the typical current draw at different clock speeds. See table 26-4 on page 225 of the datasheet.I do not know what current the PIC needs to be fed at. I was trying to determine that from the specs for the PIC.
Yes, you can get FETs which work with 3.3V devices. For example, the Si4466DY has an RDS(on) of 0.013Ω at a Vgs of 2.5V.As for the FETs, yes that was my hope. Four channels each feeding a logic FET with 3.3v.