Low Power Regulators

[andybarrett1]

Both the RTC and LCD are 5V devices - RTC min is 4.5V, LCD min is 4.7 V.
So you really can't run your circuit at 3.3 V.
You will either need to use Ioannis' suggestion (which I also recommend), or go back to your 2936 regulator with at least a 6V battery. The 9V batteries have pretty low capacity - you might be better off with a couple 3V button cells; I have not worked out the details on those.

Hi yes the present circuit is built around a 5v supply....BUT :-

Looking to upgrade using LF818/19, LCD 3.3v and different RTC ...1307 has lousy timekeeping :-(

Application remains same... just maybe different parts!

BR
Andy

[Charlie]

Hi yes the present circuit is built around a 5v supply....BUT :-

Looking to upgrade using LF818/19, LCD 3.3v and different RTC ...1307 has lousy timekeeping :-(

Application remains same... just maybe different parts!

BR
Andy

You'll need to choose those parts to know your supply tolerance. The answers are all in the data sheets.