common HD-44780 based Digital Clock - using an XLP PIC microcontroller?

[littletransistor]

Hey there,

Currently I'm using the PIC18F4221 which is used as the brains of the HD-44780-based alarm clock, with the DS1307+ RTC running. However, the 4K space had been used up, so I intend to replace the PIC18F4221 with the PIC18F45K20. (checked the datasheets - almost the same, except the memory space is more)

The thing is, this microcontroller uses 3.3V, while the rest of the stuff uses at least 5V for normal operation.

Could they be compatible? Or should I use a 3.3V voltage regulator, and then connect the output to the Vdd of the chip?

 

[Wp100]

Hi,

Its only nano watt but why not look at the 18LF4620 , it can run at 3v3 or 5v and has twice the memory of the 45K20.
If you add in another regulator its power loss kind of defeats the point of xlp

 

[Mr RB]

Just use a 18F452 or 18F4520. They are similar PICs to 18F45K20 but are the 5v version, and you need 5v for the RTC and LCD anyway.